Fix #35282: cycles color ramp set to constant interpolation did not work well.

intern/cycles/blender/blender_shader.cpp

@@ -193,6 +193,7 @@ static ShaderNode *add_node(Scene *scene, BL::BlendData b_data, BL::Scene b_scen
 		RGBRampNode *ramp = new RGBRampNode();
 		BL::ShaderNodeValToRGB b_ramp_node(b_node);
 		colorramp_to_array(b_ramp_node.color_ramp(), ramp->ramp, RAMP_TABLE_SIZE);
+		ramp->interpolate = b_ramp_node.color_ramp().interpolation() != BL::ColorRamp::interpolation_CONSTANT;
 		node = ramp;
 	}
 	else if (b_node.is_a(&RNA_ShaderNodeRGB)) {

intern/cycles/kernel/shaders/node_rgb_ramp.osl

@@ -22,6 +22,7 @@
 shader node_rgb_ramp(
 	color ramp_color[RAMP_TABLE_SIZE] = {0.0},
 	float ramp_alpha[RAMP_TABLE_SIZE] = {0.0},
+	int ramp_interpolate = 1,
 
 	float Fac = 0.0,
 	output color Color = 0.0,
@@ -38,7 +39,7 @@ shader node_rgb_ramp(
 	Color = ramp_color[i];
 	Alpha = ramp_alpha[i];
 
-	if (t > 0.0) {
+	if (ramp_interpolate && t > 0.0) {
 		Color = (1.0 - t) * Color + t * ramp_color[i + 1];
 		Alpha = (1.0 - t) * Alpha + t * ramp_alpha[i + 1];
 	}

intern/cycles/kernel/svm/svm_ramp.h

@@ -21,7 +21,7 @@
 
 CCL_NAMESPACE_BEGIN
 
-__device float4 rgb_ramp_lookup(KernelGlobals *kg, int offset, float f)
+__device float4 rgb_ramp_lookup(KernelGlobals *kg, int offset, float f, bool interpolate)
 {
 	f = clamp(f, 0.0f, 1.0f)*(RAMP_TABLE_SIZE-1);
 
@@ -31,7 +31,7 @@ __device float4 rgb_ramp_lookup(KernelGlobals *kg, int offset, float f)
 
 	float4 a = fetch_node_float(kg, offset+i);
 
-	if(t > 0.0f)
+	if(interpolate && t > 0.0f)
 		a = (1.0f - t)*a + t*fetch_node_float(kg, offset+i+1);
 
 	return a;
@@ -39,12 +39,13 @@ __device float4 rgb_ramp_lookup(KernelGlobals *kg, int offset, float f)
 
 __device void svm_node_rgb_ramp(KernelGlobals *kg, ShaderData *sd, float *stack, uint4 node, int *offset)
 {
-	uint fac_offset = node.y;
+	uint fac_offset, color_offset, alpha_offset;
-	uint color_offset = node.z;
+	uint interpolate = node.z;
-	uint alpha_offset = node.w;
+
+	decode_node_uchar4(node.y, &fac_offset, &color_offset, &alpha_offset, NULL);
 
 	float fac = stack_load_float(stack, fac_offset);
-	float4 color = rgb_ramp_lookup(kg, *offset, fac);
+	float4 color = rgb_ramp_lookup(kg, *offset, fac, interpolate);
 
 	if(stack_valid(color_offset))
 		stack_store_float3(stack, color_offset, float4_to_float3(color));
@@ -63,9 +64,9 @@ __device void svm_node_rgb_curves(KernelGlobals *kg, ShaderData *sd, float *stac
 	float fac = stack_load_float(stack, fac_offset);
 	float3 color = stack_load_float3(stack, color_offset);
 
-	float r = rgb_ramp_lookup(kg, *offset, color.x).x;
+	float r = rgb_ramp_lookup(kg, *offset, color.x, true).x;
-	float g = rgb_ramp_lookup(kg, *offset, color.y).y;
+	float g = rgb_ramp_lookup(kg, *offset, color.y, true).y;
-	float b = rgb_ramp_lookup(kg, *offset, color.z).z;
+	float b = rgb_ramp_lookup(kg, *offset, color.z, true).z;
 
 	color = (1.0f - fac)*color + fac*make_float3(r, g, b);
 	stack_store_float3(stack, out_offset, color);
@@ -82,9 +83,9 @@ __device void svm_node_vector_curves(KernelGlobals *kg, ShaderData *sd, float *s
 	float fac = stack_load_float(stack, fac_offset);
 	float3 color = stack_load_float3(stack, color_offset);
 
-	float r = rgb_ramp_lookup(kg, *offset, (color.x + 1.0f)*0.5f).x;
+	float r = rgb_ramp_lookup(kg, *offset, (color.x + 1.0f)*0.5f, true).x;
-	float g = rgb_ramp_lookup(kg, *offset, (color.y + 1.0f)*0.5f).y;
+	float g = rgb_ramp_lookup(kg, *offset, (color.y + 1.0f)*0.5f, true).y;
-	float b = rgb_ramp_lookup(kg, *offset, (color.z + 1.0f)*0.5f).z;
+	float b = rgb_ramp_lookup(kg, *offset, (color.z + 1.0f)*0.5f, true).z;
 
 	color = (1.0f - fac)*color + fac*make_float3(r*2.0f - 1.0f, g*2.0f - 1.0f, b*2.0f - 1.0f);
 	stack_store_float3(stack, out_offset, color);

intern/cycles/render/nodes.cpp

@@ -3175,6 +3175,8 @@ RGBRampNode::RGBRampNode()
 	add_input("Fac", SHADER_SOCKET_FLOAT);
 	add_output("Color", SHADER_SOCKET_COLOR);
 	add_output("Alpha", SHADER_SOCKET_FLOAT);
+
+	interpolate = true;
 }
 
 void RGBRampNode::compile(SVMCompiler& compiler)
@@ -3189,7 +3191,12 @@ void RGBRampNode::compile(SVMCompiler& compiler)
 	if(!alpha_out->links.empty())
 		compiler.stack_assign(alpha_out);
 
-	compiler.add_node(NODE_RGB_RAMP, fac_in->stack_offset, color_out->stack_offset, alpha_out->stack_offset);
+	compiler.add_node(NODE_RGB_RAMP,
+		compiler.encode_uchar4(
+			fac_in->stack_offset,
+			color_out->stack_offset,
+			alpha_out->stack_offset),
+		interpolate);
 	compiler.add_array(ramp, RAMP_TABLE_SIZE);
 }
 
@@ -3209,6 +3216,7 @@ void RGBRampNode::compile(OSLCompiler& compiler)
 
 	compiler.parameter_color_array("ramp_color", ramp_color, RAMP_TABLE_SIZE);
 	compiler.parameter_array("ramp_alpha", ramp_alpha, RAMP_TABLE_SIZE);
+	compiler.parameter("ramp_interpolate", interpolate);
 	
 	compiler.add(this, "node_rgb_ramp");
 }

intern/cycles/render/nodes.h

@@ -488,6 +488,7 @@ class RGBRampNode : public ShaderNode {
 public:
 	SHADER_NODE_CLASS(RGBRampNode)
 	float4 ramp[RAMP_TABLE_SIZE];
+	bool interpolate;
 };
 
 class SetNormalNode : public ShaderNode {