Merge branch 'master' into tmp-usd-alab-v2-T100452tmp-usd-alab-v2-T100452

1 files changed, 33 insertions, 10 deletions

diff --git a/source/blender/gpu/shaders/common/gpu_shader_common_curves.glsl b/source/blender/gpu/shaders/common/gpu_shader_common_curves.glsl
index db8e114ec7a..e68c173c055 100644
--- a/source/blender/gpu/shaders/common/gpu_shader_common_curves.glsl
+++ b/source/blender/gpu/shaders/common/gpu_shader_common_curves.glsl
@@ -26,9 +26,29 @@ vec3 extrapolate_if_needed(vec3 parameters, vec3 values, vec3 start_slopes, vec3
   return values + parameters * slopes;
 }
 
-/* Curve maps are stored in sampler objects that are evaluated in the [0, 1] range, so normalize
- * parameters accordingly. */
-#define NORMALIZE_PARAMETER(parameter, minimum, range) ((parameter - minimum) * range)
+/* Curve maps are stored in texture samplers that are evaluated in the [0, 1] range, so normalize
+ * the parameters accordingly. Additionally, ensure that the parameters evaluate the sampler at the
+ * center of the pixels, because samplers are evaluated using linear interpolation. */
+float normalize_parameter(float parameter, float minimum, float range_divider)
+{
+  float normalized_parameter = (parameter - minimum) * range_divider;
+
+  /* Curve maps have a fixed width of 257. We offset by the equivalent of half a pixel and scale
+   * down such that the normalized parameter 1.0 corresponds to the center of the last pixel. */
+  float sampler_offset = 0.5 / 257.0;
+  float sampler_scale = 1.0 - (1.0 / 257.0);
+  return normalized_parameter * sampler_scale + sampler_offset;
+}
+
+/* Same as normalize_parameter but vectorized. */
+vec3 normalize_parameters(vec3 parameters, vec3 minimums, vec3 range_dividers)
+{
+  vec3 normalized_parameters = (parameters - minimums) * range_dividers;
+
+  float sampler_offset = 0.5 / 257.0;
+  float sampler_scale = 1.0 - (1.0 / 257.0);
+  return normalized_parameters * sampler_scale + sampler_offset;
+}
 
 void curves_combined_rgb(float factor,
                          vec4 color,
@@ -46,7 +66,7 @@ void curves_combined_rgb(float factor,
 
   /* First, evaluate alpha curve map at all channels. The alpha curve is the Combined curve in the
    * UI. */
-  vec3 parameters = NORMALIZE_PARAMETER(balanced.rgb, range_minimums.aaa, range_dividers.aaa);
+  vec3 parameters = normalize_parameters(balanced.rgb, range_minimums.aaa, range_dividers.aaa);
   result.r = texture(curve_map, vec2(parameters.x, layer)).a;
   result.g = texture(curve_map, vec2(parameters.y, layer)).a;
   result.b = texture(curve_map, vec2(parameters.z, layer)).a;
@@ -55,13 +75,14 @@ void curves_combined_rgb(float factor,
   result.rgb = extrapolate_if_needed(parameters, result.rgb, start_slopes.aaa, end_slopes.aaa);
 
   /* Then, evaluate each channel on its curve map. */
-  parameters = NORMALIZE_PARAMETER(result.rgb, range_minimums.rgb, range_dividers.rgb);
+  parameters = normalize_parameters(result.rgb, range_minimums.rgb, range_dividers.rgb);
   result.r = texture(curve_map, vec2(parameters.r, layer)).r;
   result.g = texture(curve_map, vec2(parameters.g, layer)).g;
   result.b = texture(curve_map, vec2(parameters.b, layer)).b;
 
   /* Then, extrapolate again if needed. */
   result.rgb = extrapolate_if_needed(parameters, result.rgb, start_slopes.rgb, end_slopes.rgb);
+
   result.a = color.a;
 
   result = mix(color, result, factor);
@@ -83,13 +104,14 @@ void curves_combined_only(float factor,
 
   /* Evaluate alpha curve map at all channels. The alpha curve is the Combined curve in the
    * UI. */
-  vec3 parameters = NORMALIZE_PARAMETER(balanced.rgb, range_minimum, range_divider);
+  vec3 parameters = normalize_parameters(balanced.rgb, vec3(range_minimum), vec3(range_divider));
   result.r = texture(curve_map, vec2(parameters.x, layer)).a;
   result.g = texture(curve_map, vec2(parameters.y, layer)).a;
   result.b = texture(curve_map, vec2(parameters.z, layer)).a;
 
   /* Then, extrapolate if needed. */
   result.rgb = extrapolate_if_needed(parameters, result.rgb, vec3(start_slope), vec3(end_slope));
+
   result.a = color.a;
 
   result = mix(color, result, factor);
@@ -147,8 +169,8 @@ void curves_film_like(float factor,
 
   /* Evaluate alpha curve map at the maximum and minimum channels. The alpha curve is the Combined
    * curve in the UI. */
-  float min_parameter = NORMALIZE_PARAMETER(minimum, range_minimum, range_divider);
-  float max_parameter = NORMALIZE_PARAMETER(maximum, range_minimum, range_divider);
+  float min_parameter = normalize_parameter(minimum, range_minimum, range_divider);
+  float max_parameter = normalize_parameter(maximum, range_minimum, range_divider);
   float new_min = texture(curve_map, vec2(min_parameter, layer)).a;
   float new_max = texture(curve_map, vec2(max_parameter, layer)).a;
 
@@ -165,6 +187,7 @@ void curves_film_like(float factor,
   vec3 median_or_min = mix(vec3(new_median), vec3(new_min), channel_is_min);
   bvec3 channel_is_max = equal(balanced.rgb, vec3(maximum));
   result.rgb = mix(median_or_min, vec3(new_max), channel_is_max);
+
   result.a = color.a;
 
   result = mix(color, result, clamp(factor, 0.0, 1.0));
@@ -180,7 +203,7 @@ void curves_vector(vec3 vector,
                    out vec3 result)
 {
   /* Evaluate each component on its curve map. */
-  vec3 parameters = NORMALIZE_PARAMETER(vector, range_minimums, range_dividers);
+  vec3 parameters = normalize_parameters(vector, range_minimums, range_dividers);
   result.x = texture(curve_map, vec2(parameters.x, layer)).x;
   result.y = texture(curve_map, vec2(parameters.y, layer)).y;
   result.z = texture(curve_map, vec2(parameters.z, layer)).z;
@@ -214,7 +237,7 @@ void curves_float(float value,
                   out float result)
 {
   /* Evaluate the normalized value on the first curve map. */
-  float parameter = NORMALIZE_PARAMETER(value, range_minimum, range_divider);
+  float parameter = normalize_parameter(value, range_minimum, range_divider);
   result = texture(curve_map, vec2(parameter, layer)).x;
 
   /* Then, extrapolate if needed. */