1 files changed, 70 insertions, 0 deletions
diff --git a/source/blender/draw/engines/gpencil/shaders/fx/gpencil_fx_swirl_frag.glsl b/source/blender/draw/engines/gpencil/shaders/fx/gpencil_fx_swirl_frag.glsl
new file mode 100644
index 00000000000..6ce64350b3d
--- /dev/null
+++ b/source/blender/draw/engines/gpencil/shaders/fx/gpencil_fx_swirl_frag.glsl
@@ -0,0 +1,70 @@
+uniform mat4 ProjectionMatrix;
+uniform mat4 ViewMatrix;
+
+uniform sampler2D strokeColor;
+uniform sampler2D strokeDepth;
+
+uniform vec2 Viewport;
+uniform vec3 loc;
+uniform int radius;
+uniform float angle;
+uniform int transparent;
+
+uniform float pixsize;   /* rv3d->pixsize */
+uniform float pixelsize; /* U.pixelsize */
+uniform float pixfactor;
+
+out vec4 FragColor;
+
+float defaultpixsize = pixsize * pixelsize * (1000.0 / pixfactor);
+
+/* 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;
+}
+
+/* This swirl shader is a modified version of original Geeks3d.com code */
+void main()
+{
+	vec2 uv = vec2(gl_FragCoord.xy);
+	float stroke_depth;
+	vec4 outcolor;
+	
+	vec4 center3d = ProjectionMatrix * ViewMatrix * vec4(loc.xyz, 1.0); 
+	vec2 center = toScreenSpace(center3d);
+	vec2 tc = uv - center;
+
+	float dist = length(tc);
+	float pxradius = (ProjectionMatrix[3][3] == 0.0) ? (radius / (loc.z * defaultpixsize)) : (radius / defaultpixsize);
+	pxradius = max(pxradius, 1);
+	
+	if (dist <= pxradius) {
+		float percent = (pxradius - dist) / pxradius;
+		float theta = percent * percent * angle * 8.0;
+		float s = sin(theta);
+		float c = cos(theta);
+		tc = vec2(dot(tc, vec2(c, -s)), dot(tc, vec2(s, c)));
+		tc += center;
+
+		stroke_depth = texelFetch(strokeDepth, ivec2(tc), 0).r;
+		outcolor = texelFetch(strokeColor, ivec2(tc), 0);
+	}
+	else {
+		if (transparent == 1) {
+			discard;
+		}
+		stroke_depth = texelFetch(strokeDepth, ivec2(uv), 0).r;
+		outcolor = texelFetch(strokeColor, ivec2(uv), 0);
+	}
+
+	gl_FragDepth = stroke_depth;
+	FragColor = outcolor;
+}