Fix T46915: Non-intuitive behavior of Vector Curve Mapping node

Vector mapping node was doing some weird mapping of both original and mapped
coordinates. Mapping of original coordinates was caused by the clamping nature
of the LUT generated from the node. Mapping of the mapped value again was quite
totally obscure -- one needed to constantly keep in mind that actual value will
be scaled up and moved down.

This commit makes it so values in the vector curve mapping are always absolute.
In fact, it is now behaving quite the same as RGB curve mapping node and the
code could be de-duplicated. Keeping the code duplicated for a bit so it's more
clear what exact parts of the node changed.

Reviewers: brecht

Subscribers: bassamk

Differential Revision: https://developer.blender.org/D1672

intern/cycles/blender/addon/version_update.py

@@ -100,6 +100,19 @@ def mapping_node_order_flip(node):
         node.rotation = quat.to_euler('XYZ')
 
 
+def vector_curve_node_remap(node):
+    """
+    Remap values of vector curve node from normalized to absolute values
+    """
+    from mathutils import Vector
+    if node.bl_idname == 'ShaderNodeVectorCurve':
+        node.mapping.use_clip = False
+        for curve in node.mapping.curves:
+            for point in curve.points:
+                point.location.x = (point.location.x * 2.0) - 1.0
+                point.location.y = (point.location.y - 0.5) * 2.0
+        node.mapping.update()
+
 @persistent
 def do_versions(self):
     # We don't modify startup file because it assumes to
@@ -140,3 +153,6 @@ def do_versions(self):
     # Euler order was ZYX in previous versions.
     if bpy.data.version <= (2, 73, 4):
         foreach_cycles_node(mapping_node_order_flip)
+
+    if bpy.data.version <= (2, 76, 5):
+        foreach_cycles_node(vector_curve_node_remap)

intern/cycles/blender/blender_shader.cpp

@@ -231,8 +231,13 @@ static ShaderNode *add_node(Scene *scene,
 	}
 	if(b_node.is_a(&RNA_ShaderNodeVectorCurve)) {
 		BL::ShaderNodeVectorCurve b_curve_node(b_node);
+		BL::CurveMapping mapping(b_curve_node.mapping());
 		VectorCurvesNode *curves = new VectorCurvesNode();
-		curvemapping_color_to_array(b_curve_node.mapping(), curves->curves, RAMP_TABLE_SIZE, false);
+		curvemapping_color_to_array(mapping,
+		                            curves->curves,
+		                            RAMP_TABLE_SIZE,
+		                            false);
+		curvemapping_minmax(mapping, false, &curves->min_x, &curves->max_x);
 		node = curves;
 	}
 	else if(b_node.is_a(&RNA_ShaderNodeValToRGB)) {

intern/cycles/blender/blender_util.h

@@ -101,21 +101,20 @@ static inline void curvemapping_color_to_array(BL::CurveMapping cumap,
                                                bool rgb_curve)
 {
 	float min_x = 0.0f, max_x = 1.0f;
-	/* TODO(sergey): Vector curve mapping is still clipping to 0..1. */
-	if(rgb_curve) {
-		/* TODO(sergey): There is no easy way to automatically guess what is
-		 * the range to be used here for the case when mapping is applied on
-		 * top of another mapping (i.e. R curve applied on top of common
-		 * one).
-		 *
-		 * Using largest possible range form all curves works correct for the
-		 * cases like vector curves and should be good enough heuristic for
-		 * the color curves as well.
-		 *
-		 * There might be some better estimations here tho.
-		 */
-		curvemapping_minmax(cumap, rgb_curve, &min_x, &max_x);
-	}
+
+	/* TODO(sergey): There is no easy way to automatically guess what is
+	 * the range to be used here for the case when mapping is applied on
+	 * top of another mapping (i.e. R curve applied on top of common
+	 * one).
+	 *
+	 * Using largest possible range form all curves works correct for the
+	 * cases like vector curves and should be good enough heuristic for
+	 * the color curves as well.
+	 *
+	 * There might be some better estimations here tho.
+	 */
+	curvemapping_minmax(cumap, rgb_curve, &min_x, &max_x);
+
 	const float range_x = max_x - min_x;
 
 	cumap.update();

intern/cycles/kernel/shaders/node_vector_curves.osl

@@ -19,7 +19,22 @@
 
 float ramp_lookup(color ramp[RAMP_TABLE_SIZE], float at, int component)
 {
-	float f = clamp((at + 1.0) * 0.5, 0.0, 1.0) * (RAMP_TABLE_SIZE - 1);
+	if (at < 0.0 || at > 1.0) {
+		float t0, dy;
+		if(at < 0.0) {
+			t0 = ramp[0][component];
+			dy = t0 - ramp[1][component];
+			at = -at;
+		}
+		else {
+			t0 = ramp[RAMP_TABLE_SIZE - 1][component];
+			dy = t0 - ramp[RAMP_TABLE_SIZE - 2][component];
+			at = at - 1.0;
+		}
+		return t0 + dy * at * (RAMP_TABLE_SIZE - 1);
+	}
+
+	float f = clamp(at, 0.0, 1.0) * (RAMP_TABLE_SIZE - 1);
 
 	/* clamp int as well in case of NaN */
 	int i = (int)f;
@@ -32,19 +47,23 @@ float ramp_lookup(color ramp[RAMP_TABLE_SIZE], float at, int component)
 	if (t > 0.0)
 		result = (1.0 - t) * result + t * ramp[i + 1][component];
 	
-	return result * 2.0 - 1.0;
+	return result;
 }
 
 shader node_vector_curves(
 	color ramp[RAMP_TABLE_SIZE] = {0.0},
+	float min_x = 0.0,
+	float max_x = 1.0,
 
 	vector VectorIn = vector(0.0, 0.0, 0.0),
 	float Fac = 0.0,
 	output vector VectorOut = vector(0.0, 0.0, 0.0))
 {
-	VectorOut[0] = ramp_lookup(ramp, VectorIn[0], 0);
-	VectorOut[1] = ramp_lookup(ramp, VectorIn[1], 1);
-	VectorOut[2] = ramp_lookup(ramp, VectorIn[2], 2);
+	color c = (VectorIn - vector(min_x, min_x, min_x)) / (max_x - min_x);
+
+	VectorOut[0] = ramp_lookup(ramp, c[0], 0);
+	VectorOut[1] = ramp_lookup(ramp, c[1], 1);
+	VectorOut[2] = ramp_lookup(ramp, c[2], 2);
 
 	VectorOut = mix(VectorIn, VectorOut, Fac);
 }

intern/cycles/kernel/svm/svm_ramp.h

@@ -101,18 +101,26 @@ ccl_device void svm_node_rgb_curves(KernelGlobals *kg, ShaderData *sd, float *st
 
 ccl_device void svm_node_vector_curves(KernelGlobals *kg, ShaderData *sd, float *stack, uint4 node, int *offset)
 {
-	uint fac_offset = node.y;
-	uint color_offset = node.z;
-	uint out_offset = node.w;
+	uint fac_offset, color_offset, out_offset;
+	decode_node_uchar4(node.y,
+	                   &fac_offset,
+	                   &color_offset,
+	                   &out_offset,
+	                   NULL);
 
 	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, true, false).x;
-	float g = rgb_ramp_lookup(kg, *offset, (color.y + 1.0f)*0.5f, true, false).y;
-	float b = rgb_ramp_lookup(kg, *offset, (color.z + 1.0f)*0.5f, true, false).z;
+	const float min_x = __int_as_float(node.z),
+	            max_x = __int_as_float(node.w);
+	const float range_x = max_x - min_x;
+	color = (color - make_float3(min_x, min_x, min_x)) / range_x;
 
-	color = (1.0f - fac)*color + fac*make_float3(r*2.0f - 1.0f, g*2.0f - 1.0f, b*2.0f - 1.0f);
+	float r = rgb_ramp_lookup(kg, *offset, color.x, true, true).x;
+	float g = rgb_ramp_lookup(kg, *offset, color.y, true, true).y;
+	float b = rgb_ramp_lookup(kg, *offset, color.z, true, true).z;
+
+	color = (1.0f - fac)*color + fac*make_float3(r, g, b);
 	stack_store_float3(stack, out_offset, color);
 
 	*offset += RAMP_TABLE_SIZE;

intern/cycles/render/nodes.cpp

@@ -4443,6 +4443,9 @@ VectorCurvesNode::VectorCurvesNode()
 	add_input("Fac", SHADER_SOCKET_FLOAT);
 	add_input("Vector", SHADER_SOCKET_VECTOR);
 	add_output("Vector", SHADER_SOCKET_VECTOR);
+
+	min_x = 0.0f;
+	max_x = 1.0f;
 }
 
 void VectorCurvesNode::compile(SVMCompiler& compiler)
@@ -4455,7 +4458,12 @@ void VectorCurvesNode::compile(SVMCompiler& compiler)
 	compiler.stack_assign(vector_in);
 	compiler.stack_assign(vector_out);
 
-	compiler.add_node(NODE_VECTOR_CURVES, fac_in->stack_offset, vector_in->stack_offset, vector_out->stack_offset);
+	compiler.add_node(NODE_VECTOR_CURVES,
+	                  compiler.encode_uchar4(fac_in->stack_offset,
+	                                         vector_in->stack_offset,
+	                                         vector_out->stack_offset),
+	                  __float_as_int(min_x),
+	                  __float_as_int(max_x));
 	compiler.add_array(curves, RAMP_TABLE_SIZE);
 }
 
@@ -4470,6 +4478,8 @@ void VectorCurvesNode::compile(OSLCompiler& compiler)
 	}
 
 	compiler.parameter_color_array("ramp", ramp, RAMP_TABLE_SIZE);
+	compiler.parameter("min_x", min_x);
+	compiler.parameter("max_x", max_x);
 	compiler.add(this, "node_vector_curves");
 }
 

intern/cycles/render/nodes.h

@@ -946,6 +946,7 @@ public:
 	virtual bool equals(const ShaderNode * /*other*/) { return false; }
 
 	float4 curves[RAMP_TABLE_SIZE];
+	float min_x, max_x;
 };
 
 class RGBRampNode : public ShaderNode {

source/blender/blenkernel/BKE_blender.h

@@ -45,7 +45,7 @@ extern "C" {
 #define BLENDER_SUBVERSION      5
 /* Several breakages with 270, e.g. constraint deg vs rad */
 #define BLENDER_MINVERSION      270
-#define BLENDER_MINSUBVERSION   5
+#define BLENDER_MINSUBVERSION   6
 
 /* used by packaging tools */
 /* can be left blank, otherwise a,b,c... etc with no quotes */