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

3 files changed, 23 insertions, 0 deletions

diff --git a/source/blender/gpu/CMakeLists.txt b/source/blender/gpu/CMakeLists.txt
index 2ff72266a64..f1ffd7827b8 100644
--- a/source/blender/gpu/CMakeLists.txt
+++ b/source/blender/gpu/CMakeLists.txt
@@ -275,6 +275,7 @@ data_to_c_simple(shaders/material/gpu_shader_material_anisotropic.glsl SRC)
 data_to_c_simple(shaders/material/gpu_shader_material_attribute.glsl SRC)
 data_to_c_simple(shaders/material/gpu_shader_material_background.glsl SRC)
 data_to_c_simple(shaders/material/gpu_shader_material_bevel.glsl SRC)
+data_to_c_simple(shaders/material/gpu_shader_material_wavelength.glsl SRC)
 data_to_c_simple(shaders/material/gpu_shader_material_blackbody.glsl SRC)
 data_to_c_simple(shaders/material/gpu_shader_material_bright_contrast.glsl SRC)
 data_to_c_simple(shaders/material/gpu_shader_material_bump.glsl SRC)
diff --git a/source/blender/gpu/intern/gpu_material_library.c b/source/blender/gpu/intern/gpu_material_library.c
index 175facc0a8d..3c216c1a991 100644
--- a/source/blender/gpu/intern/gpu_material_library.c
+++ b/source/blender/gpu/intern/gpu_material_library.c
@@ -47,6 +47,7 @@ extern char datatoc_gpu_shader_material_anisotropic_glsl[];
 extern char datatoc_gpu_shader_material_attribute_glsl[];
 extern char datatoc_gpu_shader_material_background_glsl[];
 extern char datatoc_gpu_shader_material_bevel_glsl[];
+extern char datatoc_gpu_shader_material_wavelength_glsl[];
 extern char datatoc_gpu_shader_material_blackbody_glsl[];
 extern char datatoc_gpu_shader_material_bright_contrast_glsl[];
 extern char datatoc_gpu_shader_material_bump_glsl[];
@@ -191,6 +192,11 @@ static GPUMaterialLibrary gpu_shader_material_bevel_library = {
     .dependencies = {NULL},
 };
 
+static GPUMaterialLibrary gpu_shader_material_wavelength_library = {
+    .code = datatoc_gpu_shader_material_wavelength_glsl,
+    .dependencies = {NULL},
+};
+
 static GPUMaterialLibrary gpu_shader_material_blackbody_library = {
     .code = datatoc_gpu_shader_material_blackbody_glsl,
     .dependencies = {NULL},
@@ -593,6 +599,7 @@ static GPUMaterialLibrary *gpu_material_libraries[] = {
     &gpu_shader_material_attribute_library,
     &gpu_shader_material_background_library,
     &gpu_shader_material_bevel_library,
+    &gpu_shader_material_wavelength_library,
     &gpu_shader_material_blackbody_library,
     &gpu_shader_material_bright_contrast_library,
     &gpu_shader_material_bump_library,
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);
+}