Support voronoi texture in GLSL shading

It gives some slight differences on the plane corners, but can't
really figure out source of the issue here yet.

It's still better than fully white texture for the previews anyway.

At this point we should perhaps ifdef chunks of the code in order
to have faster GLSL compilation and probably even faster compiled
code. Will look into this shortly.

source/blender/gpu/shaders/gpu_shader_material.glsl

@@ -2329,6 +2329,57 @@ int floor_to_int(float x)
 	return int(floor(x));
 }
 
+uint hash(uint kx, uint ky, uint kz)
+{
+#define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
+#define final(a,b,c) \
+{ \
+	c ^= b; c -= rot(b,14); \
+	a ^= c; a -= rot(c,11); \
+	b ^= a; b -= rot(a,25); \
+	c ^= b; c -= rot(b,16); \
+	a ^= c; a -= rot(c,4);  \
+	b ^= a; b -= rot(a,14); \
+	c ^= b; c -= rot(b,24); \
+}
+	// now hash the data!
+	uint a, b, c, len = 3u;
+	a = b = c = 0xdeadbeefu + (len << 2u) + 13u;
+
+	c += kz;
+	b += ky;
+	a += kx;
+	final(a, b, c);
+
+	return c;
+#undef rot
+#undef final
+}
+
+float bits_to_01(uint bits)
+{
+	float x = float(bits) * (1.0 / float(0xffffffffu));
+	return x;
+}
+
+float cellnoise(vec3 p)
+{
+	int ix = floor_to_int(p.x);
+	int iy = floor_to_int(p.y);
+	int iz = floor_to_int(p.z);
+
+	return bits_to_01(hash(uint(ix), uint(iy), uint(iz)));
+}
+
+vec3 cellnoise_color(vec3 p)
+{
+	float r = cellnoise(p);
+	float g = cellnoise(vec3(p.y, p.x, p.z));
+	float b = cellnoise(vec3(p.y, p.z, p.x));
+
+	return vec3(r, g, b);
+}
+
 /*********** NEW SHADER NODES ***************/
 
 #define NUM_LIGHTS 3
@@ -2828,10 +2879,72 @@ void node_tex_sky(vec3 co, out vec4 color)
 	color = vec4(1.0);
 }
 
-void node_tex_voronoi(vec3 co, float scale, out vec4 color, out float fac)
+void node_tex_voronoi(vec3 co, float scale, float coloring, out vec4 color, out float fac)
 {
-	color = vec4(1.0);
-	fac = 1.0;
+	vec3 p = co * scale;
+	int xx, yy, zz, xi, yi, zi;
+	float da[4];
+	vec3 pa[4];
+
+	xi = floor_to_int(p[0]);
+	yi = floor_to_int(p[1]);
+	zi = floor_to_int(p[2]);
+
+	da[0] = 1e+10;
+	da[1] = 1e+10;
+	da[2] = 1e+10;
+	da[3] = 1e+10;
+
+	for (xx = xi - 1; xx <= xi + 1; xx++) {
+		for (yy = yi - 1; yy <= yi + 1; yy++) {
+			for (zz = zi - 1; zz <= zi + 1; zz++) {
+				vec3 ip = vec3(xx, yy, zz);
+				vec3 vp = cellnoise_color(ip);
+				vec3 pd = p - (vp + ip);
+				float d = dot(pd, pd);
+				vp += vec3(xx, yy, zz);
+				if (d < da[0]) {
+					da[3] = da[2];
+					da[2] = da[1];
+					da[1] = da[0];
+					da[0] = d;
+					pa[3] = pa[2];
+					pa[2] = pa[1];
+					pa[1] = pa[0];
+					pa[0] = vp;
+				}
+				else if (d < da[1]) {
+					da[3] = da[2];
+					da[2] = da[1];
+					da[1] = d;
+
+					pa[3] = pa[2];
+					pa[2] = pa[1];
+					pa[1] = vp;
+				}
+				else if (d < da[2]) {
+					da[3] = da[2];
+					da[2] = d;
+
+					pa[3] = pa[2];
+					pa[2] = vp;
+				}
+				else if (d < da[3]) {
+					da[3] = d;
+					pa[3] = vp;
+				}
+			}
+		}
+	}
+
+	if (coloring == 0.0) {
+		fac = abs(da[0]);
+		color = vec4(fac, fac, fac, 1);
+	}
+	else {
+		color = vec4(cellnoise_color(pa[0]), 1);
+		fac = (color.x + color.y + color.z) * (1.0 / 3.0);
+	}
 }
 
 void node_tex_wave(vec3 co, float scale, float distortion, float detail, float detail_scale, out vec4 color, out float fac)

source/blender/nodes/shader/nodes/node_shader_tex_voronoi.c

@@ -53,12 +53,17 @@ static void node_shader_init_tex_voronoi(bNodeTree *UNUSED(ntree), bNode *node)
 
 static int node_shader_gpu_tex_voronoi(GPUMaterial *mat, bNode *node, bNodeExecData *UNUSED(execdata), GPUNodeStack *in, GPUNodeStack *out)
 {
-	if (!in[0].link)
+	if (!in[0].link) {
 		in[0].link = GPU_attribute(CD_ORCO, "");
+		GPU_link(mat, "generated_from_orco", in[0].link, &in[0].link);
+	}
 
 	node_shader_gpu_tex_mapping(mat, node, in, out);
 
-	return GPU_stack_link(mat, "node_tex_voronoi", in, out);
+	NodeTexVoronoi *tex = (NodeTexVoronoi *)node->storage;
+	float coloring = tex->coloring;
+
+	return GPU_stack_link(mat, "node_tex_voronoi", in, out, GPU_uniform(&coloring));
 }
 
 /* node type definition */