GP: implement Shadow FX (wip)

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

2 files changed, 154 insertions, 0 deletions

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;
+}