EEVEE: Refactor curve nodes

This patches rewrites the GPU shaders of curve nodes for easier future
development. This is a non-functional change. The new code avoids code
duplication by moving common code into BKE curve mapping functions. It
also avoids ambiguous data embedding into the gradient vectors that are
passed to vectors and reduces the size of uniforms uploaded to the
shader by avoiding redundancies.

This is needed in preparation for the viewport compositor, which will
utilize and extend this implementation.

Reviewed By: fclem

Differential Revision: https://developer.blender.org/D14689

1 files changed, 30 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_colortools.h b/source/blender/blenkernel/BKE_colortools.h
index 0d4560207ea..d52fd91ccdd 100644
--- a/source/blender/blenkernel/BKE_colortools.h
+++ b/source/blender/blenkernel/BKE_colortools.h
@@ -129,6 +129,36 @@ bool BKE_curvemapping_RGBA_does_something(const struct CurveMapping *cumap);
 void BKE_curvemapping_table_F(const struct CurveMapping *cumap, float **array, int *size);
 void BKE_curvemapping_table_RGBA(const struct CurveMapping *cumap, float **array, int *size);
 
+/** Get the minimum x value of each curve map table. */
+void BKE_curvemapping_get_range_minimums(const struct CurveMapping *curve_mapping,
+                                         float minimums[4]);
+
+/** Get the reciprocal of the difference between the maximum and the minimum x value of each curve
+ * map table. Evaluation parameters can be multiplied by this value to be normalized. If the
+ * difference is zero, 1^8 is returned. */
+void BKE_curvemapping_compute_range_dividers(const struct CurveMapping *curve_mapping,
+                                             float dividers[4]);
+
+/** Compute the slopes at the start and end points of each curve map. The slopes are multiplied by
+ * the range of the curve map to compensate for parameter normalization. If the slope is vertical,
+ * 1^8 is returned.  */
+void BKE_curvemapping_compute_slopes(const struct CurveMapping *curve_mapping,
+                                     float start_slopes[4],
+                                     float end_slopes[4]);
+
+/** Check if the curve map at the index is identity, that is, does nothing. A curve map is said to
+ * be identity if:
+ * - The curve mapping uses extrapolation.
+ * - Its range is 1.
+ * - The slope at its start point is 1.
+ * - The slope at its end point is 1.
+ * - The number of points is 2.
+ * - The start point is at (0, 0).
+ * - The end point is at (1, 1).
+ * Note that this could return false even if the curve map is identity, this happens in the case
+ * when more than 2 points exist in the curve map but all points are collinear. */
+bool BKE_curvemapping_is_map_identity(const struct CurveMapping *curve_mapping, int index);
+
 /**
  * Call when you do images etc, needs restore too. also verifies tables.
  * non-const (these modify the curve).