From 72ec5dd096a3110e8085919f4c0e3320ef176657 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Tue, 30 Jan 2024 22:13:56 +0000
Subject: Adjust light view projection matrix upfront

Saves doing it per pixel, per region later
---
 gfx/gl/sceneRenderer.cpp           | 8 +++++++-
 gfx/gl/shaders/directionalLight.fs | 8 ++++----
 2 files changed, 11 insertions(+), 5 deletions(-)

(limited to 'gfx/gl')

diff --git a/gfx/gl/sceneRenderer.cpp b/gfx/gl/sceneRenderer.cpp
index 2dd1760..517d51e 100644
--- a/gfx/gl/sceneRenderer.cpp
+++ b/gfx/gl/sceneRenderer.cpp
@@ -137,14 +137,20 @@ SceneRenderer::DirectionalLightProgram::DirectionalLightProgram() :
 {
 }
 
+const auto toTextureSpaceMat = glm::translate(glm::identity<glm::mat4>(), glm::vec3 {0.5F})
+		* glm::scale(glm::identity<glm::mat4>(), glm::vec3 {0.5F});
+
 void
 SceneRenderer::DirectionalLightProgram::setDirectionalLight(
 		const RGB & c, const Direction3D & d, const GlobalPosition3D & p, const std::span<const glm::mat4x4> lvp) const
 {
+	const auto toTextureSpace = [](const glm::mat4 & m) {
+		return toTextureSpaceMat * m;
+	};
 	glUniform(colourLoc, c);
 	const auto nd = glm::normalize(d);
 	glUniform(directionLoc, nd);
 	glUniform(lightPointLoc, p);
 	glUniform(lightViewProjectionCountLoc, static_cast<GLuint>(lvp.size()));
-	glUniform(lightViewProjectionLoc, lvp);
+	glUniform(lightViewProjectionLoc, std::span<const glm::mat4> {lvp * toTextureSpace});
 }
diff --git a/gfx/gl/shaders/directionalLight.fs b/gfx/gl/shaders/directionalLight.fs
index c49bb8d..24457b8 100644
--- a/gfx/gl/shaders/directionalLight.fs
+++ b/gfx/gl/shaders/directionalLight.fs
@@ -19,18 +19,18 @@ uniform uint lightViewProjectionCount;
 
 const vec3 e1 = vec3(0, 0, 0), e2 = vec3(1, 1, 1);
 
-	float
+float
 insideShadowCube(vec3 v)
 {
 	const vec3 s = step(e1, v) - step(e2, v);
 	return s.x * s.y * s.z;
 }
 
-	float
+float
 isShaded(vec4 Position)
 {
 	for (uint m = 0u; m < lightViewProjectionCount; m++) {
-		const vec3 PositionInLightSpace = (lightViewProjection[m] * Position).xyz * .5 + .5;
+		const vec3 PositionInLightSpace = (lightViewProjection[m] * Position).xyz;
 		const float inside = insideShadowCube(PositionInLightSpace);
 		if (inside > 0) {
 			const float lightSpaceDepth = texture(shadowMap, vec3(PositionInLightSpace.xy, m)).r;
@@ -40,7 +40,7 @@ isShaded(vec4 Position)
 	return 0;
 }
 
-	void
+void
 main()
 {
 	const vec4 Position = vec4(texture(gPosition, TexCoords).xyz - lightPoint, 1);
-- 
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