Viewport smoke: add support to render the volume using a color ramp.

This is yet another debug option that allows to render an arbitrary
simulation field by using a color ramp to inspect its voxel values.
Note that when using this, fire rendering is turned off.

Reviewers: plasmasolutions, gottfried

Differential Revision: https://developer.blender.org/D1733

3 files changed, 26 insertions, 0 deletions

diff --git a/source/blender/gpu/GPU_shader.h b/source/blender/gpu/GPU_shader.h
index 762329ee077..5b94db6e120 100644
--- a/source/blender/gpu/GPU_shader.h
+++ b/source/blender/gpu/GPU_shader.h
@@ -89,6 +89,7 @@ typedef enum GPUBuiltinShader {
 	GPU_SHADER_SEP_GAUSSIAN_BLUR = 1,
 	GPU_SHADER_SMOKE             = 2,
 	GPU_SHADER_SMOKE_FIRE        = 3,
+	GPU_SHADER_SMOKE_COBA        = 4,
 } GPUBuiltinShader;
 
 GPUShader *GPU_shader_get_builtin_shader(GPUBuiltinShader shader);
diff --git a/source/blender/gpu/intern/gpu_shader.c b/source/blender/gpu/intern/gpu_shader.c
index 5cfb323bc4b..14f2764b009 100644
--- a/source/blender/gpu/intern/gpu_shader.c
+++ b/source/blender/gpu/intern/gpu_shader.c
@@ -68,6 +68,7 @@ static struct GPUShadersGlobal {
 		GPUShader *sep_gaussian_blur;
 		GPUShader *smoke;
 		GPUShader *smoke_fire;
+		GPUShader *smoke_coba;
 		/* cache for shader fx. Those can exist in combinations so store them here */
 		GPUShader *fx_shaders[MAX_FX_SHADERS * 2];
 	} shaders;
@@ -623,6 +624,13 @@ GPUShader *GPU_shader_get_builtin_shader(GPUBuiltinShader shader)
 				        NULL, NULL, NULL, 0, 0, 0);
 			retval = GG.shaders.smoke_fire;
 			break;
+		case GPU_SHADER_SMOKE_COBA:
+			if (!GG.shaders.smoke_coba)
+				GG.shaders.smoke_coba = GPU_shader_create(
+				        datatoc_gpu_shader_smoke_vert_glsl, datatoc_gpu_shader_smoke_frag_glsl,
+				        NULL, NULL, "#define USE_COBA;\n", 0, 0, 0);
+			retval = GG.shaders.smoke_coba;
+			break;
 	}
 
 	if (retval == NULL)
@@ -734,6 +742,11 @@ void GPU_shader_free_builtin_shaders(void)
 		GG.shaders.smoke_fire = NULL;
 	}
 
+	if (GG.shaders.smoke_coba) {
+		GPU_shader_free(GG.shaders.smoke_coba);
+		GG.shaders.smoke_coba = NULL;
+	}
+
 	for (i = 0; i < 2 * MAX_FX_SHADERS; ++i) {
 		if (GG.shaders.fx_shaders[i]) {
 			GPU_shader_free(GG.shaders.fx_shaders[i]);
diff --git a/source/blender/gpu/shaders/gpu_shader_smoke_frag.glsl b/source/blender/gpu/shaders/gpu_shader_smoke_frag.glsl
index fd790009e02..6ded453225e 100644
--- a/source/blender/gpu/shaders/gpu_shader_smoke_frag.glsl
+++ b/source/blender/gpu/shaders/gpu_shader_smoke_frag.glsl
@@ -8,10 +8,17 @@ uniform float density_scale;
 uniform sampler3D soot_texture;
 uniform sampler3D shadow_texture;
 
+#ifdef USE_COBA
+uniform sampler1D transfer_texture;
+uniform sampler3D color_band_texture;
+#endif
+
 void main()
 {
 	/* compute color and density from volume texture */
 	vec4 soot = texture3D(soot_texture, coords);
+
+#ifndef USE_COBA
 	vec3 soot_color;
 	if (soot.a != 0) {
 		soot_color = active_color * soot.rgb / soot.a;
@@ -31,6 +38,11 @@ void main()
 
 	/* premultiply alpha */
 	vec4 color = vec4(soot_alpha * soot_color, soot_alpha);
+#else
+	float color_band = texture3D(color_band_texture, coords).r;
+	vec4 transfer_function = texture1D(transfer_texture, color_band);
+	vec4 color = transfer_function * density_scale;
+#endif
 
 	gl_FragColor = color;
 }