Fix the viewport transform of world to shadow texcoords.

Math is hard.

2 files changed, 5 insertions, 4 deletions

diff --git a/ground.c b/ground.c
index 558452b..382d0dd 100644
--- a/ground.c
+++ b/ground.c
@@ -62,11 +62,11 @@ install_ground_transform(void)
 	 */
 	memcpy(&temp, &gluIdentityMatrix, sizeof(gluIdentityMatrix));
 	temp.col[0].values[0] = (1.0 - 0.0) / 2.0;
-	temp.col[0].values[3] = temp.col[0].values[0] + 0.0;
+	temp.col[3].values[0] = temp.col[0].values[0] + 0.0;
 	temp.col[1].values[1] = (1.0 - 0.0) / 2.0;
-	temp.col[1].values[3] = temp.col[1].values[1] + 0.0;
+	temp.col[3].values[1] = temp.col[1].values[1] + 0.0;
 	temp.col[2].values[2] = (1.0 - 0.0) / 2.0;
-	temp.col[2].values[3] = (1.0 - 0.0) / 2.0;
+	temp.col[3].values[2] = (1.0 - 0.0) / 2.0;
 
 	gluMult4m_4m(&world_to_shadow_texcoords, &temp, &world_to_light_ndc);
 
diff --git a/ground.vert b/ground.vert
index f4d7713..4fbfe4d 100644
--- a/ground.vert
+++ b/ground.vert
@@ -15,7 +15,8 @@ void main()
 */
 	gl_Position = mvp * gl_Vertex;
 	vertex_eye = vec3(mv * gl_Vertex);
-	shadow_coords = (light_mvp * gl_Vertex).xy;
+	vec4 temp = light_mvp * gl_Vertex;
+	shadow_coords = (temp).xy / temp.w;
 /*
 	mat3 tbn = mat3(t,
 			cross(n, t),