Eevee Wavelength Node Support

This patch adds wavelength node support to Eevee, similar to how
Eevee Blackbody node works, thus it is a little off from Cycles.

Reviewed By: #eevee_viewport, fclem, brecht
Differential Revision: https://developer.blender.org/D11326

1 files changed, 15 insertions, 0 deletions

diff --git a/source/blender/gpu/shaders/material/gpu_shader_material_wavelength.glsl b/source/blender/gpu/shaders/material/gpu_shader_material_wavelength.glsl
new file mode 100644
index 00000000000..2c5d38eabbe
--- /dev/null
+++ b/source/blender/gpu/shaders/material/gpu_shader_material_wavelength.glsl
@@ -0,0 +1,15 @@
+void node_wavelength(float wavelength,
+                     sampler1DArray spectrummap,
+                     float layer,
+                     vec3 xyz_to_r,
+                     vec3 xyz_to_g,
+                     vec3 xyz_to_b,
+                     out vec4 color)
+{
+  mat3 xyz_to_rgb = mat3(xyz_to_r, xyz_to_g, xyz_to_b);
+  float t = (wavelength - 380.0) / (780.0 - 380.0);
+  vec3 xyz = texture(spectrummap, vec2(t, layer)).rgb;
+  vec3 rgb = xyz * xyz_to_rgb;
+  rgb *= 1.0 / 2.52; /* Empirical scale from lg to make all comps <= 1. */
+  color = vec4(clamp(rgb, 0.0, 1.0), 1.0);
+}