GP: implement Shadow FX (wip)

Initial implementation of effect to create a drop shadow of the strokes

13 files changed, 525 insertions, 16 deletions

diff --git a/source/blender/draw/CMakeLists.txt b/source/blender/draw/CMakeLists.txt
index 06752e41092..a2ab6383828 100644
--- a/source/blender/draw/CMakeLists.txt
+++ b/source/blender/draw/CMakeLists.txt
@@ -340,6 +340,8 @@ data_to_c_simple(engines/gpencil/shaders/fx/gpencil_fx_light_frag.glsl SRC)
 data_to_c_simple(engines/gpencil/shaders/fx/gpencil_fx_pixel_frag.glsl SRC)
 data_to_c_simple(engines/gpencil/shaders/fx/gpencil_fx_rim_prepare_frag.glsl SRC)
 data_to_c_simple(engines/gpencil/shaders/fx/gpencil_fx_rim_resolve_frag.glsl SRC)
+data_to_c_simple(engines/gpencil/shaders/fx/gpencil_fx_shadow_prepare_frag.glsl SRC)
+data_to_c_simple(engines/gpencil/shaders/fx/gpencil_fx_shadow_resolve_frag.glsl SRC)
 data_to_c_simple(engines/gpencil/shaders/fx/gpencil_fx_swirl_frag.glsl SRC)
 data_to_c_simple(engines/gpencil/shaders/fx/gpencil_fx_wave_frag.glsl SRC)
 
diff --git a/source/blender/draw/engines/gpencil/gpencil_engine.c b/source/blender/draw/engines/gpencil/gpencil_engine.c
index 657c7665312..bc545a1db80 100644
--- a/source/blender/draw/engines/gpencil/gpencil_engine.c
+++ b/source/blender/draw/engines/gpencil/gpencil_engine.c
@@ -141,17 +141,17 @@ static void GPENCIL_create_framebuffers(void *vedata)
 		            GPU_ATTACHMENT_TEXTURE(e_data.temp_color_tx_b)
 		        });
 
-		/* used for rim FX effect */
-		e_data.temp_depth_tx_rim = DRW_texture_pool_query_2D(
+		/* used for rim and shadow FX effects */
+		e_data.temp_depth_tx_fx = DRW_texture_pool_query_2D(
 		        size[0], size[1], GPU_DEPTH24_STENCIL8,
 		        &draw_engine_gpencil_type);
-		e_data.temp_color_tx_rim = DRW_texture_pool_query_2D(
+		e_data.temp_color_tx_fx = DRW_texture_pool_query_2D(
 		        size[0], size[1], fb_format,
 		        &draw_engine_gpencil_type);
 		GPU_framebuffer_ensure_config(
-		        &fbl->temp_fb_rim, {
-		            GPU_ATTACHMENT_TEXTURE(e_data.temp_depth_tx_rim),
-		            GPU_ATTACHMENT_TEXTURE(e_data.temp_color_tx_rim),
+		        &fbl->temp_fb_fx, {
+		            GPU_ATTACHMENT_TEXTURE(e_data.temp_depth_tx_fx),
+		            GPU_ATTACHMENT_TEXTURE(e_data.temp_color_tx_fx),
 		        });
 
 		/* background framebuffer to speed up drawing process (always 16 bits) */
diff --git a/source/blender/draw/engines/gpencil/gpencil_engine.h b/source/blender/draw/engines/gpencil/gpencil_engine.h
index be883360959..89a50170eb6 100644
--- a/source/blender/draw/engines/gpencil/gpencil_engine.h
+++ b/source/blender/draw/engines/gpencil/gpencil_engine.h
@@ -72,6 +72,7 @@ typedef struct tGPencilObjectCache {
 	DRWShadingGroup *fx_colorize_sh;
 	DRWShadingGroup *fx_pixel_sh;
 	DRWShadingGroup *fx_rim_sh;
+	DRWShadingGroup *fx_shadow_sh;
 	DRWShadingGroup *fx_swirl_sh;
 	DRWShadingGroup *fx_flip_sh;
 	DRWShadingGroup *fx_light_sh;
@@ -160,7 +161,7 @@ typedef struct GPENCIL_FramebufferList {
 	struct GPUFrameBuffer *main;
 	struct GPUFrameBuffer *temp_fb_a;
 	struct GPUFrameBuffer *temp_fb_b;
-	struct GPUFrameBuffer *temp_fb_rim;
+	struct GPUFrameBuffer *temp_fb_fx;
 	struct GPUFrameBuffer *background_fb;
 
 	struct GPUFrameBuffer *multisample_fb;
@@ -234,6 +235,8 @@ typedef struct GPENCIL_e_data {
 	struct GPUShader *gpencil_fx_pixel_sh;
 	struct GPUShader *gpencil_fx_rim_prepare_sh;
 	struct GPUShader *gpencil_fx_rim_resolve_sh;
+	struct GPUShader *gpencil_fx_shadow_prepare_sh;
+	struct GPUShader *gpencil_fx_shadow_resolve_sh;
 	struct GPUShader *gpencil_fx_swirl_sh;
 	struct GPUShader *gpencil_fx_wave_sh;
 
@@ -254,8 +257,8 @@ typedef struct GPENCIL_e_data {
 	struct GPUTexture *temp_color_tx_b;
 	struct GPUTexture *temp_depth_tx_b;
 
-	struct GPUTexture *temp_color_tx_rim;
-	struct GPUTexture *temp_depth_tx_rim;
+	struct GPUTexture *temp_color_tx_fx;
+	struct GPUTexture *temp_depth_tx_fx;
 
 	/* for buffer only one batch is nedeed because the drawing is only of one stroke */
 	GPUBatch *batch_buffer_stroke;
diff --git a/source/blender/draw/engines/gpencil/gpencil_shader_fx.c b/source/blender/draw/engines/gpencil/gpencil_shader_fx.c
index 7d6a8691b87..5a96d6d1275 100644
--- a/source/blender/draw/engines/gpencil/gpencil_shader_fx.c
+++ b/source/blender/draw/engines/gpencil/gpencil_shader_fx.c
@@ -48,6 +48,8 @@ extern char datatoc_gpencil_fx_light_frag_glsl[];
 extern char datatoc_gpencil_fx_pixel_frag_glsl[];
 extern char datatoc_gpencil_fx_rim_prepare_frag_glsl[];
 extern char datatoc_gpencil_fx_rim_resolve_frag_glsl[];
+extern char datatoc_gpencil_fx_shadow_prepare_frag_glsl[];
+extern char datatoc_gpencil_fx_shadow_resolve_frag_glsl[];
 extern char datatoc_gpencil_fx_swirl_frag_glsl[];
 extern char datatoc_gpencil_fx_wave_frag_glsl[];
 
@@ -407,8 +409,8 @@ static void DRW_gpencil_fx_rim(
 	        e_data->gpencil_fx_blur_sh,
 	        psl->fx_shader_pass_blend);
 	DRW_shgroup_call_add(fx_shgrp, fxquad, NULL);
-	DRW_shgroup_uniform_texture_ref(fx_shgrp, "strokeColor", &e_data->temp_color_tx_rim);
-	DRW_shgroup_uniform_texture_ref(fx_shgrp, "strokeDepth", &e_data->temp_depth_tx_rim);
+	DRW_shgroup_uniform_texture_ref(fx_shgrp, "strokeColor", &e_data->temp_color_tx_fx);
+	DRW_shgroup_uniform_texture_ref(fx_shgrp, "strokeDepth", &e_data->temp_depth_tx_fx);
 	DRW_shgroup_uniform_int(fx_shgrp, "blur", &fxd->blur[0], 2);
 
 	DRW_shgroup_uniform_vec3(fx_shgrp, "loc", &cache->loc[0], 1);
@@ -425,13 +427,82 @@ static void DRW_gpencil_fx_rim(
 	DRW_shgroup_call_add(fx_shgrp, fxquad, NULL);
 	DRW_shgroup_uniform_texture_ref(fx_shgrp, "strokeColor", &e_data->temp_color_tx_a);
 	DRW_shgroup_uniform_texture_ref(fx_shgrp, "strokeDepth", &e_data->temp_depth_tx_a);
-	DRW_shgroup_uniform_texture_ref(fx_shgrp, "strokeRim", &e_data->temp_color_tx_rim);
+	DRW_shgroup_uniform_texture_ref(fx_shgrp, "strokeRim", &e_data->temp_color_tx_fx);
 	DRW_shgroup_uniform_vec3(fx_shgrp, "mask_color", &fxd->mask_rgb[0], 1);
 	DRW_shgroup_uniform_int(fx_shgrp, "mode", &fxd->mode, 1);
 
 	fxd->runtime.fx_sh_c = fx_shgrp;
 }
 
+/* Shadow FX */
+static void DRW_gpencil_fx_shadow(
+	ShaderFxData *fx, GPENCIL_e_data *e_data, GPENCIL_Data *vedata,
+	tGPencilObjectCache *cache)
+{
+	if (fx == NULL) {
+		return;
+	}
+	ShadowShaderFxData *fxd = (ShadowShaderFxData *)fx;
+	if ((!fxd->object) && (fxd->flag & FX_SHADOW_USE_OBJECT)) {
+		return;
+	}
+
+	GPENCIL_StorageList *stl = ((GPENCIL_Data *)vedata)->stl;
+	GPENCIL_PassList *psl = ((GPENCIL_Data *)vedata)->psl;
+	DRWShadingGroup *fx_shgrp;
+
+	struct GPUBatch *fxquad = DRW_cache_fullscreen_quad_get();
+	/* prepare pass */
+	fx_shgrp = DRW_shgroup_create(
+		e_data->gpencil_fx_shadow_prepare_sh,
+		psl->fx_shader_pass_blend);
+	DRW_shgroup_call_add(fx_shgrp, fxquad, NULL);
+	DRW_shgroup_uniform_texture_ref(fx_shgrp, "strokeColor", &e_data->temp_color_tx_a);
+	DRW_shgroup_uniform_texture_ref(fx_shgrp, "strokeDepth", &e_data->temp_depth_tx_a);
+	DRW_shgroup_uniform_vec2(fx_shgrp, "Viewport", DRW_viewport_size_get(), 1);
+
+	DRW_shgroup_uniform_int(fx_shgrp, "offset", &fxd->offset[0], 2);
+	DRW_shgroup_uniform_float(fx_shgrp, "scale", &fxd->scale[0], 2);
+	DRW_shgroup_uniform_float(fx_shgrp, "rotation", &fxd->rotation, 1);
+	DRW_shgroup_uniform_vec4(fx_shgrp, "shadow_color", &fxd->shadow_rgba[0], 1);
+
+	if ((fxd->object) && (fxd->flag & FX_SHADOW_USE_OBJECT)) {
+		DRW_shgroup_uniform_vec3(fx_shgrp, "loc", &fxd->object->loc[0], 1);
+	}
+	else {
+		DRW_shgroup_uniform_vec3(fx_shgrp, "loc", &cache->loc[0], 1);
+	}
+
+	const int nowave = -1;
+	if (fxd->flag & FX_SHADOW_USE_WAVE) {
+		DRW_shgroup_uniform_int(fx_shgrp, "orientation", &fxd->orientation, 1);
+	}
+	else {
+		DRW_shgroup_uniform_int(fx_shgrp, "orientation", &nowave, 1);
+	}
+	DRW_shgroup_uniform_float(fx_shgrp, "amplitude", &fxd->amplitude, 1);
+	DRW_shgroup_uniform_float(fx_shgrp, "period", &fxd->period, 1);
+	DRW_shgroup_uniform_float(fx_shgrp, "phase", &fxd->phase, 1);
+
+	DRW_shgroup_uniform_float(fx_shgrp, "pixsize", stl->storage->pixsize, 1);
+	DRW_shgroup_uniform_float(fx_shgrp, "pixelsize", &U.pixelsize, 1);
+	DRW_shgroup_uniform_float(fx_shgrp, "pixfactor", &cache->pixfactor, 1);
+
+	fxd->runtime.fx_sh = fx_shgrp;
+
+	/* resolve pass */
+	fx_shgrp = DRW_shgroup_create(
+		e_data->gpencil_fx_shadow_resolve_sh,
+		psl->fx_shader_pass_blend);
+	DRW_shgroup_call_add(fx_shgrp, fxquad, NULL);
+	DRW_shgroup_uniform_texture_ref(fx_shgrp, "strokeColor", &e_data->temp_color_tx_a);
+	DRW_shgroup_uniform_texture_ref(fx_shgrp, "strokeDepth", &e_data->temp_depth_tx_a);
+	DRW_shgroup_uniform_texture_ref(fx_shgrp, "shadowColor", &e_data->temp_color_tx_fx);
+	DRW_shgroup_uniform_texture_ref(fx_shgrp, "shadowDepth", &e_data->temp_depth_tx_fx);
+
+	fxd->runtime.fx_sh_b = fx_shgrp;
+}
+
 /* Swirl FX */
 static void DRW_gpencil_fx_swirl(
         ShaderFxData *fx, GPENCIL_e_data *e_data, GPENCIL_Data *vedata,
@@ -531,6 +602,13 @@ void GPENCIL_create_fx_shaders(GPENCIL_e_data *e_data)
 		e_data->gpencil_fx_rim_resolve_sh = DRW_shader_create_fullscreen(
 			datatoc_gpencil_fx_rim_resolve_frag_glsl, NULL);
 	}
+	if (!e_data->gpencil_fx_shadow_prepare_sh) {
+		e_data->gpencil_fx_shadow_prepare_sh = DRW_shader_create_fullscreen(
+			datatoc_gpencil_fx_shadow_prepare_frag_glsl, NULL);
+
+		e_data->gpencil_fx_shadow_resolve_sh = DRW_shader_create_fullscreen(
+			datatoc_gpencil_fx_shadow_resolve_frag_glsl, NULL);
+	}
 	if (!e_data->gpencil_fx_swirl_sh) {
 		e_data->gpencil_fx_swirl_sh = DRW_shader_create_fullscreen(
 			datatoc_gpencil_fx_swirl_frag_glsl, NULL);
@@ -551,6 +629,8 @@ void GPENCIL_delete_fx_shaders(GPENCIL_e_data *e_data)
 	DRW_SHADER_FREE_SAFE(e_data->gpencil_fx_pixel_sh);
 	DRW_SHADER_FREE_SAFE(e_data->gpencil_fx_rim_prepare_sh);
 	DRW_SHADER_FREE_SAFE(e_data->gpencil_fx_rim_resolve_sh);
+	DRW_SHADER_FREE_SAFE(e_data->gpencil_fx_shadow_prepare_sh);
+	DRW_SHADER_FREE_SAFE(e_data->gpencil_fx_shadow_resolve_sh);
 	DRW_SHADER_FREE_SAFE(e_data->gpencil_fx_swirl_sh);
 	DRW_SHADER_FREE_SAFE(e_data->gpencil_fx_wave_sh);
 }
@@ -602,6 +682,9 @@ void DRW_gpencil_fx_prepare(
 				case eShaderFxType_Rim:
 					DRW_gpencil_fx_rim(fx, e_data, vedata, cache);
 					break;
+				case eShaderFxType_Shadow:
+					DRW_gpencil_fx_shadow(fx, e_data, vedata, cache);
+					break;
 				case eShaderFxType_Swirl:
 					DRW_gpencil_fx_swirl(fx, e_data, vedata, cache);
 					break;
@@ -706,8 +789,8 @@ static void draw_gpencil_rim_blur(
 		fxd->runtime.fx_sh_b, fxd->runtime.fx_sh_b);
 
 	/* copy pass from b for ping-pong frame buffers */
-	GPU_framebuffer_bind(fbl->temp_fb_rim);
-	GPU_framebuffer_clear_color_depth(fbl->temp_fb_rim, clearcol, 1.0f);
+	GPU_framebuffer_bind(fbl->temp_fb_fx);
+	GPU_framebuffer_clear_color_depth(fbl->temp_fb_fx, clearcol, 1.0f);
 	DRW_draw_pass(psl->mix_pass_noblend);
 }
 
@@ -729,8 +812,8 @@ static void draw_gpencil_rim_passes(
 	int by = fxd->blur[1];
 
 	/* prepare mask */
-	GPU_framebuffer_bind(fbl->temp_fb_rim);
-	GPU_framebuffer_clear_color_depth(fbl->temp_fb_rim, clearcol, 1.0f);
+	GPU_framebuffer_bind(fbl->temp_fb_fx);
+	GPU_framebuffer_clear_color_depth(fbl->temp_fb_fx, clearcol, 1.0f);
 	DRW_draw_pass_subset(
 	        psl->fx_shader_pass_blend,
 	        fxd->runtime.fx_sh, fxd->runtime.fx_sh);
@@ -772,6 +855,44 @@ static void draw_gpencil_rim_passes(
 	DRW_draw_pass(psl->mix_pass_noblend);
 }
 
+/* helper to draw SHADOW passes */
+static void draw_gpencil_shadow_passes(
+	struct GPENCIL_e_data *e_data,
+	struct GPENCIL_Data *vedata,
+	struct ShadowShaderFxData *fxd)
+{
+	if (fxd->runtime.fx_sh_b == NULL) {
+		return;
+	}
+
+	GPENCIL_PassList *psl = ((GPENCIL_Data *)vedata)->psl;
+	GPENCIL_FramebufferList *fbl = ((GPENCIL_Data *)vedata)->fbl;
+
+	static float clearcol[4] = { 0.0f, 0.0f, 0.0f, 0.0f };
+
+	/* prepare shadow */
+	GPU_framebuffer_bind(fbl->temp_fb_fx);
+	GPU_framebuffer_clear_color_depth(fbl->temp_fb_fx, clearcol, 1.0f);
+	DRW_draw_pass_subset(
+		psl->fx_shader_pass_blend,
+		fxd->runtime.fx_sh, fxd->runtime.fx_sh);
+
+	/* resolve */
+	GPU_framebuffer_bind(fbl->temp_fb_b);
+	GPU_framebuffer_clear_color_depth(fbl->temp_fb_b, clearcol, 1.0f);
+	DRW_draw_pass_subset(
+		psl->fx_shader_pass_blend,
+		fxd->runtime.fx_sh_b, fxd->runtime.fx_sh_b);
+
+	/* copy pass from b to a for ping-pong frame buffers */
+	e_data->input_depth_tx = e_data->temp_depth_tx_b;
+	e_data->input_color_tx = e_data->temp_color_tx_b;
+
+	GPU_framebuffer_bind(fbl->temp_fb_a);
+	GPU_framebuffer_clear_color_depth(fbl->temp_fb_a, clearcol, 1.0f);
+	DRW_draw_pass(psl->mix_pass_noblend);
+}
+
 /* apply all object fx effects */
 void DRW_gpencil_fx_draw(
         struct GPENCIL_e_data *e_data,
@@ -822,6 +943,12 @@ void DRW_gpencil_fx_draw(
 					draw_gpencil_rim_passes(e_data, vedata, fxd);
 					break;
 				}
+				case eShaderFxType_Shadow:
+				{
+					ShadowShaderFxData *fxd = (ShadowShaderFxData *)fx;
+					draw_gpencil_shadow_passes(e_data, vedata, fxd);
+					break;
+				}
 				case eShaderFxType_Swirl:
 				{
 					SwirlShaderFxData *fxd = (SwirlShaderFxData *)fx;
diff --git a/source/blender/draw/engines/gpencil/shaders/fx/gpencil_fx_shadow_prepare_frag.glsl b/source/blender/draw/engines/gpencil/shaders/fx/gpencil_fx_shadow_prepare_frag.glsl
new file mode 100644
index 00000000000..941b746d494
--- /dev/null
+++ b/source/blender/draw/engines/gpencil/shaders/fx/gpencil_fx_shadow_prepare_frag.glsl
@@ -0,0 +1,122 @@
+uniform mat4 ProjectionMatrix;
+uniform mat4 ViewMatrix;
+
+/* ******************************************************************* */
+/* create shadow                                                       */
+/* ******************************************************************* */
+uniform sampler2D strokeColor;
+uniform sampler2D strokeDepth;
+uniform vec2 Viewport;
+
+uniform int offset[2];
+uniform float scale[2];
+uniform float rotation;
+uniform vec4 shadow_color;
+
+uniform float amplitude;
+uniform float period;
+uniform float phase;
+uniform int orientation;
+
+uniform vec3 loc;
+uniform float pixsize;   /* rv3d->pixsize */
+uniform float pixelsize; /* U.pixelsize */
+uniform float pixfactor;
+
+#define M_PI 3.1415926535897932384626433832795
+
+#define HORIZONTAL 0
+#define VERTICAL 1
+
+float defaultpixsize = pixsize * pixelsize * (1000.0 / pixfactor);
+vec2 noffset = vec2(offset[0], offset[1]);
+
+out vec4 FragColor;
+
+/* project 3d point to 2d on screen space */
+vec2 toScreenSpace(vec4 vertex)
+{
+	/* need to calculate ndc because this is not done by vertex shader */
+	vec3 ndc = vec3(vertex).xyz / vertex.w;
+
+	vec2 sc;
+	sc.x = ((ndc.x + 1.0) / 2.0) * Viewport.x;
+	sc.y = ((ndc.y + 1.0) / 2.0) * Viewport.y;
+
+	return sc;
+}
+
+void main()
+{
+	vec2 uv = vec2(gl_FragCoord.xy);
+	vec4 nloc = ProjectionMatrix * ViewMatrix * vec4(loc.xyz, 1.0);
+	vec2 loc2d = toScreenSpace(nloc);
+
+	float dx = (ProjectionMatrix[3][3] == 0.0) ? (noffset[0] / (nloc.z * defaultpixsize)) : (noffset[0] / defaultpixsize);
+	float dy = (ProjectionMatrix[3][3] == 0.0) ? (noffset[1] / (nloc.z * defaultpixsize)) : (noffset[1] / defaultpixsize);
+
+	/* move point to new coords system */
+	vec2 tpos = vec2(uv.x, uv.y) - loc2d;
+
+	/* apply offset */
+	tpos = vec2(tpos.x - dx, tpos.y - dy);
+	
+	/* apply scale */
+	tpos.x *= 1.0 / scale[0];
+	tpos.y *= 1.0 / scale[1];
+	
+	/* rotation */
+	tpos.x = (tpos.x * cos(rotation)) - (tpos.y * sin(rotation));
+	tpos.y = (tpos.x * sin(rotation)) + (tpos.y * cos(rotation));
+	
+	/* back to original coords system */
+	vec2 texpos = tpos + loc2d;
+	
+	/* wave */ 
+	float value;
+	if (orientation == HORIZONTAL) {
+		float pval = (uv.x * M_PI) / Viewport[0];
+		value = amplitude * sin((period * pval) + phase);
+		texpos.y += value;
+	}
+	else if (orientation == VERTICAL){
+		float pval = (uv.y * M_PI) / Viewport[1];
+		value = amplitude * sin((period * pval) + phase);
+		texpos.x += value;
+	}
+	
+	float stroke_depth = texelFetch(strokeDepth, ivec2(texpos.x, texpos.y), 0).r;
+	vec4 src_pixel= texelFetch(strokeColor, ivec2(texpos.x, texpos.y), 0);
+	vec4 outcolor;
+	outcolor = shadow_color;
+
+	/* is transparent */
+	if (src_pixel.a == 0.0f) {
+		discard;
+	}
+	
+	
+	
+	// /* check inside viewport */
+	// else if ((uv.x - dx < 0) || (uv.x - dx > Viewport[0])) {
+		// discard;
+	// }
+	// else if ((uv.y - dy < 0) || (uv.y - dy > Viewport[1])) {
+		// discard;
+	// }
+	// /* pixel is equal to mask color, keep */
+	// else if (src_pixel.rgb == mask_color.rgb) {
+		// discard;
+	// }
+	// else {
+		// if ((src_pixel.a > 0) && (offset_pixel.a > 0)) {
+			// discard;
+		// }
+		// else {
+			// outcolor = vec4(rim_color, 1.0);
+		// }
+	// }
+
+	gl_FragDepth = stroke_depth;
+	FragColor = outcolor;
+}
diff --git a/source/blender/draw/engines/gpencil/shaders/fx/gpencil_fx_shadow_resolve_frag.glsl b/source/blender/draw/engines/gpencil/shaders/fx/gpencil_fx_shadow_resolve_frag.glsl
new file mode 100644
index 00000000000..633dcf1fd63
--- /dev/null
+++ b/source/blender/draw/engines/gpencil/shaders/fx/gpencil_fx_shadow_resolve_frag.glsl
@@ -0,0 +1,32 @@
+/* ******************************************************************* */
+/* Resolve Shadow pass                                                 */
+/* ******************************************************************* */
+uniform sampler2D strokeColor;
+uniform sampler2D strokeDepth;
+uniform sampler2D shadowColor;
+uniform sampler2D shadowDepth;
+
+out vec4 FragColor;
+
+void main()
+{
+	ivec2 uv = ivec2(gl_FragCoord.xy);
+
+	float stroke_depth = texelFetch(strokeDepth, uv.xy, 0).r;
+	float shadow_depth = texelFetch(shadowDepth, uv.xy, 0).r;
+	vec4 stroke_pixel= texelFetch(strokeColor, uv.xy, 0);
+	vec4 shadow_pixel= texelFetch(shadowColor, uv.xy, 0);
+
+	/* copy original pixel */
+	vec4 outcolor = stroke_pixel;
+	float outdepth = stroke_depth;
+
+	/* if stroke is not on top, copy shadow */
+	if ((stroke_pixel.a <= 0.2) && (shadow_pixel.a > 0.0))  {
+		outcolor = shadow_pixel;
+		outdepth = shadow_depth;
+	}
+	
+	gl_FragDepth = outdepth;
+	FragColor = outcolor;
+}
diff --git a/source/blender/makesdna/DNA_shader_fx_types.h b/source/blender/makesdna/DNA_shader_fx_types.h
index f3c9f06c8dc..62a1d705f3b 100644
--- a/source/blender/makesdna/DNA_shader_fx_types.h
+++ b/source/blender/makesdna/DNA_shader_fx_types.h
@@ -44,6 +44,7 @@ typedef enum ShaderFxType {
 	eShaderFxType_Wave      = 6,
 	eShaderFxType_Rim       = 7,
 	eShaderFxType_Colorize  = 8,
+	eShaderFxType_Shadow    = 9,
 	NUM_SHADER_FX_TYPES
 } ShaderFxType;
 
@@ -169,6 +170,26 @@ typedef enum RimShaderFxModes {
 	eShaderFxRimMode_Divide = 5,
 } RimShaderFxModes;
 
+typedef struct ShadowShaderFxData {
+	ShaderFxData shaderfx;
+	struct Object *object;
+	int offset[2];
+	int flag;                    /* flags */
+	float shadow_rgba[4];
+	float amplitude;
+	float period;
+	float phase;
+	int orientation;
+	float scale[2];
+	float rotation;
+	ShaderFxData_runtime runtime;
+} ShadowShaderFxData;
+
+typedef enum eShadowShaderFx_Flag {
+	FX_SHADOW_USE_OBJECT = (1 << 0),
+	FX_SHADOW_USE_WAVE   = (1 << 1),
+} eShadowShaderFx_Flag;
+
 typedef struct SwirlShaderFxData {
 	ShaderFxData shaderfx;
 	struct Object *object;
diff --git a/source/blender/makesrna/RNA_access.h b/source/blender/makesrna/RNA_access.h
index 55bd83ece69..1278f27af75 100644
--- a/source/blender/makesrna/RNA_access.h
+++ b/source/blender/makesrna/RNA_access.h
@@ -621,6 +621,7 @@ extern StructRNA RNA_ShaderFxFlip;
 extern StructRNA RNA_ShaderFxLight;
 extern StructRNA RNA_ShaderFxPixel;
 extern StructRNA RNA_ShaderFxRim;
+extern StructRNA RNA_ShaderFxShadow;
 extern StructRNA RNA_ShaderFxSwirl;
 extern StructRNA RNA_ShaderFxWave;
 extern StructRNA RNA_TexMapping;
diff --git a/source/blender/makesrna/intern/rna_shader_fx.c b/source/blender/makesrna/intern/rna_shader_fx.c
index 2c09cfa787e..97acc47f2f4 100644
--- a/source/blender/makesrna/intern/rna_shader_fx.c
+++ b/source/blender/makesrna/intern/rna_shader_fx.c
@@ -55,6 +55,7 @@ const EnumPropertyItem rna_enum_object_shaderfx_type_items[] = {
 	{eShaderFxType_Light, "FX_LIGHT", ICON_SHADERFX, "Light", "Simulate ilumination" },
 	{eShaderFxType_Pixel, "FX_PIXEL", ICON_SHADERFX, "Pixelate", "Pixelate image"},
 	{eShaderFxType_Rim, "FX_RIM", ICON_SHADERFX, "Rim", "Add a rim to the image" },
+	{eShaderFxType_Shadow, "FX_SHADOW", ICON_SHADERFX, "Shadow", "Create a shadow effect"},
 	{eShaderFxType_Swirl, "FX_SWIRL", ICON_SHADERFX, "Swirl", "Create a rotation distortion"},
 	{eShaderFxType_Wave, "FX_WAVE", ICON_SHADERFX, "Wave Distortion", "Apply sinusoidal deformation"},
 	{0, NULL, 0, NULL, NULL}
@@ -101,6 +102,8 @@ static StructRNA *rna_ShaderFx_refine(struct PointerRNA *ptr)
 			return &RNA_ShaderFxPixel;
 		case eShaderFxType_Rim:
 			return &RNA_ShaderFxRim;
+		case eShaderFxType_Shadow:
+			return &RNA_ShaderFxShadow;
 		case eShaderFxType_Swirl:
 			return &RNA_ShaderFxSwirl;
 		case eShaderFxType_Flip:
@@ -180,6 +183,7 @@ static void rna_##_type##ShaderFx_##_prop##_set(PointerRNA *ptr, PointerRNA valu
 }
 
 RNA_FX_OBJECT_SET(Light, object, OB_EMPTY);
+RNA_FX_OBJECT_SET(Shadow, object, OB_EMPTY);
 RNA_FX_OBJECT_SET(Swirl, object, OB_EMPTY);
 
 #undef RNA_FX_OBJECT_SET
@@ -382,6 +386,89 @@ static void rna_def_shader_fx_rim(BlenderRNA *brna)
 	RNA_def_property_update(prop, NC_OBJECT | ND_MODIFIER, "rna_ShaderFx_update");
 }
 
+static void rna_def_shader_fx_shadow(BlenderRNA *brna)
+{
+	static EnumPropertyItem prop_shaderfx_shadow_type_items[] = {
+		{ 0, "HORIZONTAL", 0, "Horizontal", "" },
+		{ 1, "VERTICAL", 0, "Vertical", "" },
+		{ 0, NULL, 0, NULL, NULL }
+	};
+
+	StructRNA *srna;
+	PropertyRNA *prop;
+
+	srna = RNA_def_struct(brna, "ShaderFxShadow", "ShaderFx");
+	RNA_def_struct_ui_text(srna, "Shadow Effect", "Shadow effect");
+	RNA_def_struct_sdna(srna, "ShadowShaderFxData");
+	RNA_def_struct_ui_icon(srna, ICON_SHADERFX);
+
+	prop = RNA_def_property(srna, "object", PROP_POINTER, PROP_NONE);
+	RNA_def_property_ui_text(prop, "Object", "Object to determine center of rotation");
+	RNA_def_property_pointer_funcs(prop, NULL, "rna_ShadowShaderFx_object_set", NULL, NULL);
+	RNA_def_property_flag(prop, PROP_EDITABLE | PROP_ID_SELF_CHECK);
+	RNA_def_property_update(prop, 0, "rna_ShaderFx_dependency_update");
+
+	prop = RNA_def_property(srna, "offset", PROP_INT, PROP_PIXEL);
+	RNA_def_property_int_sdna(prop, NULL, "offset");
+	RNA_def_property_range(prop, -INT_MAX, INT_MAX);
+	RNA_def_property_ui_text(prop, "Offset", "Offset of the shadow");
+	RNA_def_property_update(prop, NC_OBJECT | ND_MODIFIER, "rna_ShaderFx_update");
+
+	prop = RNA_def_property(srna, "scale", PROP_FLOAT, PROP_NONE);
+	RNA_def_property_float_sdna(prop, NULL, "scale");
+	RNA_def_property_range(prop, -FLT_MAX, FLT_MAX);
+	RNA_def_property_ui_text(prop, "Scale", "Offset of the shadow");
+	RNA_def_property_update(prop, NC_OBJECT | ND_MODIFIER, "rna_ShaderFx_update");
+
+	prop = RNA_def_property(srna, "shadow_color", PROP_FLOAT, PROP_COLOR_GAMMA);
+	RNA_def_property_range(prop, 0.0, 1.0);
+	RNA_def_property_float_sdna(prop, NULL, "shadow_rgba");
+	RNA_def_property_array(prop, 4);
+	RNA_def_property_ui_text(prop, "Shadow Color", "Color used for Shadow");
+	RNA_def_property_update(prop, NC_OBJECT | ND_MODIFIER, "rna_ShaderFx_update");
+
+	prop = RNA_def_property(srna, "orientation", PROP_ENUM, PROP_NONE);
+	RNA_def_property_enum_sdna(prop, NULL, "orientation");
+	RNA_def_property_enum_items(prop, prop_shaderfx_shadow_type_items);
+	RNA_def_property_ui_text(prop, "Orientation", "Direction of the wave");
+	RNA_def_property_update(prop, NC_OBJECT | ND_MODIFIER, "rna_ShaderFx_update");
+
+	prop = RNA_def_property(srna, "amplitude", PROP_FLOAT, PROP_NONE);
+	RNA_def_property_float_sdna(prop, NULL, "amplitude");
+	RNA_def_property_range(prop, 0, FLT_MAX);
+	RNA_def_property_ui_text(prop, "Amplitude", "Amplitude of Wave");
+	RNA_def_property_update(prop, NC_OBJECT | ND_MODIFIER, "rna_ShaderFx_update");
+
+	prop = RNA_def_property(srna, "period", PROP_FLOAT, PROP_NONE);
+	RNA_def_property_float_sdna(prop, NULL, "period");
+	RNA_def_property_range(prop, 0, FLT_MAX);
+	RNA_def_property_ui_text(prop, "Period", "Period of Wave");
+	RNA_def_property_update(prop, NC_OBJECT | ND_MODIFIER, "rna_ShaderFx_update");
+
+	prop = RNA_def_property(srna, "phase", PROP_FLOAT, PROP_NONE);
+	RNA_def_property_float_sdna(prop, NULL, "phase");
+	RNA_def_property_range(prop, -FLT_MAX, FLT_MAX);
+	RNA_def_property_ui_text(prop, "Phase", "Phase Shift of Wave");
+	RNA_def_property_update(prop, NC_OBJECT | ND_MODIFIER, "rna_ShaderFx_update");
+
+	prop = RNA_def_property(srna, "rotation", PROP_FLOAT, PROP_ANGLE);
+	RNA_def_property_float_sdna(prop, NULL, "rotation");
+	RNA_def_property_range(prop, DEG2RAD(-360), DEG2RAD(360));
+	RNA_def_property_ui_range(prop, DEG2RAD(-360), DEG2RAD(360), 5, 2);
+	RNA_def_property_ui_text(prop, "Rotation", "Rotation around center or object");
+	RNA_def_property_update(prop, NC_OBJECT | ND_MODIFIER, "rna_ShaderFx_update");
+
+	prop = RNA_def_property(srna, "use_object", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_sdna(prop, NULL, "flag", FX_SHADOW_USE_OBJECT);
+	RNA_def_property_ui_text(prop, "Use Object", "Use object as center of rotation");
+	RNA_def_property_update(prop, NC_OBJECT | ND_MODIFIER, "rna_ShaderFx_update");
+
+	prop = RNA_def_property(srna, "use_wave", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_sdna(prop, NULL, "flag", FX_SHADOW_USE_WAVE);
+	RNA_def_property_ui_text(prop, "Wave", "Use wave effect");
+	RNA_def_property_update(prop, NC_OBJECT | ND_MODIFIER, "rna_ShaderFx_update");
+}
+
 static void rna_def_shader_fx_swirl(BlenderRNA *brna)
 {
 	StructRNA *srna;
@@ -529,6 +616,7 @@ void RNA_def_shader_fx(BlenderRNA *brna)
 	rna_def_shader_fx_wave(brna);
 	rna_def_shader_fx_pixel(brna);
 	rna_def_shader_fx_rim(brna);
+	rna_def_shader_fx_shadow(brna);
 	rna_def_shader_fx_swirl(brna);
 	rna_def_shader_fx_flip(brna);
 	rna_def_shader_fx_light(brna);
diff --git a/source/blender/shader_fx/CMakeLists.txt b/source/blender/shader_fx/CMakeLists.txt
index dacc0b3f063..89defbd4ac7 100644
--- a/source/blender/shader_fx/CMakeLists.txt
+++ b/source/blender/shader_fx/CMakeLists.txt
@@ -49,6 +49,7 @@ set(SRC
 	intern/FX_shader_light.c
 	intern/FX_shader_pixel.c
 	intern/FX_shader_rim.c
+	intern/FX_shader_shadow.c
 	intern/FX_shader_swirl.c
 	intern/FX_shader_wave.c
 
diff --git a/source/blender/shader_fx/FX_shader_types.h b/source/blender/shader_fx/FX_shader_types.h
index b8d8f04e07f..57b9ae71146 100644
--- a/source/blender/shader_fx/FX_shader_types.h
+++ b/source/blender/shader_fx/FX_shader_types.h
@@ -38,6 +38,7 @@ extern ShaderFxTypeInfo shaderfx_Type_Flip;
 extern ShaderFxTypeInfo shaderfx_Type_Light;
 extern ShaderFxTypeInfo shaderfx_Type_Pixel;
 extern ShaderFxTypeInfo shaderfx_Type_Rim;
+extern ShaderFxTypeInfo shaderfx_Type_Shadow;
 extern ShaderFxTypeInfo shaderfx_Type_Swirl;
 extern ShaderFxTypeInfo shaderfx_Type_Wave;
 
diff --git a/source/blender/shader_fx/intern/FX_shader_shadow.c b/source/blender/shader_fx/intern/FX_shader_shadow.c
new file mode 100644
index 00000000000..d0a2ffd4590
--- /dev/null
+++ b/source/blender/shader_fx/intern/FX_shader_shadow.c
@@ -0,0 +1,110 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software  Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * The Original Code is Copyright (C) 2018, Blender Foundation
+ * This is a new part of Blender
+ *
+ * Contributor(s): Antonio Vazquez
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ *
+ */
+
+/** \file blender/shader_fx/intern/FX_shader_shadow.c
+ *  \ingroup shader_fx
+ */
+
+#include <stdio.h>
+
+#include "DNA_scene_types.h"
+#include "DNA_object_types.h"
+#include "DNA_gpencil_types.h"
+
+#include "BLI_math_base.h"
+#include "BLI_utildefines.h"
+
+#include "BKE_library_query.h"
+#include "BKE_modifier.h"
+#include "BKE_shader_fx.h"
+
+#include "FX_shader_types.h"
+
+#include "DEG_depsgraph.h"
+#include "DEG_depsgraph_build.h"
+
+static void initData(ShaderFxData *md)
+{
+	ShadowShaderFxData *gpfx = (ShadowShaderFxData *)md;
+	gpfx->rotation = 0.0f;
+	ARRAY_SET_ITEMS(gpfx->offset, 15, 20);
+	ARRAY_SET_ITEMS(gpfx->scale, 1.0f, 1.0f);
+	ARRAY_SET_ITEMS(gpfx->shadow_rgba, 0.54f, 0.62f, 1.0f, 0.9f);
+
+	gpfx->amplitude = 10.0f;
+	gpfx->period = 20.0f;
+	gpfx->phase = 0.0f;
+	gpfx->orientation = 1;
+}
+
+static void copyData(const ShaderFxData *md, ShaderFxData *target)
+{
+	BKE_shaderfx_copyData_generic(md, target);
+}
+
+static void updateDepsgraph(ShaderFxData *fx, const ModifierUpdateDepsgraphContext *ctx)
+{
+	ShadowShaderFxData *fxd = (ShadowShaderFxData *)fx;
+	if (fxd->object != NULL) {
+		DEG_add_object_relation(ctx->node, fxd->object, DEG_OB_COMP_GEOMETRY, "Shadow ShaderFx");
+		DEG_add_object_relation(ctx->node, fxd->object, DEG_OB_COMP_TRANSFORM, "Shadow ShaderFx");
+	}
+	DEG_add_object_relation(ctx->node, ctx->object, DEG_OB_COMP_TRANSFORM, "Shadow ShaderFx");
+}
+
+static bool isDisabled(ShaderFxData *fx, int UNUSED(userRenderParams))
+{
+	ShadowShaderFxData *fxd = (ShadowShaderFxData *)fx;
+
+	return (!fxd->object) && (fxd->flag & FX_SHADOW_USE_OBJECT);
+}
+
+static void foreachObjectLink(
+	ShaderFxData *fx, Object *ob,
+	ShaderFxObjectWalkFunc walk, void *userData)
+{
+	ShadowShaderFxData *fxd = (ShadowShaderFxData *)fx;
+
+	walk(userData, ob, &fxd->object, IDWALK_CB_NOP);
+}
+
+ShaderFxTypeInfo shaderfx_Type_Shadow = {
+	/* name */              "Shadow",
+	/* structName */        "ShadowShaderFxData",
+	/* structSize */        sizeof(ShadowShaderFxData),
+	/* type */              eShaderFxType_GpencilType,
+	/* flags */             0,
+
+	/* copyData */          copyData,
+
+	/* initData */          initData,
+	/* freeData */          NULL,
+	/* isDisabled */        isDisabled,
+	/* updateDepsgraph */   updateDepsgraph,
+	/* dependsOnTime */     NULL,
+	/* foreachObjectLink */ foreachObjectLink,
+	/* foreachIDLink */     NULL,
+};
diff --git a/source/blender/shader_fx/intern/FX_shader_util.c b/source/blender/shader_fx/intern/FX_shader_util.c
index 64a1553adec..d5cbdc69ba3 100644
--- a/source/blender/shader_fx/intern/FX_shader_util.c
+++ b/source/blender/shader_fx/intern/FX_shader_util.c
@@ -49,6 +49,7 @@ void shaderfx_type_init(ShaderFxTypeInfo *types[])
 	INIT_FX_TYPE(Light);
 	INIT_FX_TYPE(Pixel);
 	INIT_FX_TYPE(Rim);
+	INIT_FX_TYPE(Shadow);
 	INIT_FX_TYPE(Swirl);
 	INIT_FX_TYPE(Wave);
 #undef INIT_FX_TYPE