From dbd90f7d607ae99c5eb5427dcf14cd5915952894 Mon Sep 17 00:00:00 2001
From: Eric Anholt <eric@anholt.net>
Date: Fri, 31 Jul 2009 17:17:49 -0700
Subject: Use shadow mapping instead of shadow texturing.

---
 ground.frag  |  9 +++++----
 ground.vert  |  4 ++--
 shadow_map.c | 40 +++++++++++++++++++++++++++++-----------
 3 files changed, 36 insertions(+), 17 deletions(-)

diff --git a/ground.frag b/ground.frag
index 8af0fb5..b5a733a 100644
--- a/ground.frag
+++ b/ground.frag
@@ -1,12 +1,13 @@
 uniform vec3 light_eye;
-varying vec3 shadow_coords;
+varying vec4 shadow_coords;
 varying vec3 vertex_eye;
-uniform sampler2D shadow_sampler;
+uniform sampler2DShadow shadow_sampler;
 
 void main()
 {
 	vec3 normal = vec3(0.0, 0.0, 1.0);
-	vec4 material_color = texture2DProj(shadow_sampler, shadow_coords);
+	vec4 material_color = vec4(1.0, 0.7, 0.5, 1.0);
+	float shadow = shadow2DProj(shadow_sampler, shadow_coords).x;
 	vec3 l = normalize(light_eye - vertex_eye);
 	vec3 v = normalize(-vertex_eye);
 	vec3 h = normalize(l + v);
@@ -14,5 +15,5 @@ void main()
 	vec3 diffuse = material_color.xyz * n_dot_l;
 	float specular = pow(dot(normal, h), 16.0);
 	gl_FragColor = step(0.0, n_dot_l) *
-	vec4(diffuse + vec3(specular), material_color.w);
+	vec4((diffuse + vec3(specular)) * shadow, material_color.w);
 }
diff --git a/ground.vert b/ground.vert
index 4ed0a26..5403df1 100644
--- a/ground.vert
+++ b/ground.vert
@@ -5,7 +5,7 @@ varying vec3 eye_surf;
 varying vec3 tangent_surf;
 */
 varying vec3 vertex_eye;
-varying vec3 shadow_coords;
+varying vec4 shadow_coords;
 uniform mat4 mvp, mv, light_mvp;
 
 void main()
@@ -15,7 +15,7 @@ void main()
 */
 	gl_Position = mvp * gl_Vertex;
 	vertex_eye = vec3(mv * gl_Vertex);
-	shadow_coords = (light_mvp * gl_Vertex).xyw;
+	shadow_coords = light_mvp * gl_Vertex;
 /*
 	mat3 tbn = mat3(t,
 			cross(n, t),
diff --git a/shadow_map.c b/shadow_map.c
index 073ec6a..5fc8777 100644
--- a/shadow_map.c
+++ b/shadow_map.c
@@ -101,6 +101,7 @@ generate_rings_shadowmap(void)
 {
 	int instance;
 	int shadow_width = 256, shadow_height = 256;
+	GLboolean first_time = GL_FALSE;
 
 	if (shadow_prog == 0)
 		return;
@@ -110,8 +111,6 @@ generate_rings_shadowmap(void)
 	calculate_light_projection();
 
 	if (shadow_tex == 0) {
-		GLenum status;
-
 		glGenTextures(1, &shadow_tex);
 		glBindTexture(GL_TEXTURE_2D, shadow_tex);
 		glTexParameteri(GL_TEXTURE_2D,
@@ -122,30 +121,47 @@ generate_rings_shadowmap(void)
 				GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
 		glTexParameteri(GL_TEXTURE_2D,
 				GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
-		glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8,
+		glTexParameteri(GL_TEXTURE_2D,
+				GL_TEXTURE_COMPARE_MODE,
+				GL_COMPARE_R_TO_TEXTURE);
+		glTexParameteri(GL_TEXTURE_2D,
+				GL_TEXTURE_COMPARE_FUNC,
+				GL_LEQUAL);
+
+		glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT,
 			     shadow_width, shadow_height, 0,
-			     GL_RGBA, GL_FLOAT, NULL);
+			     GL_DEPTH_COMPONENT, GL_FLOAT, NULL);
 
 		glGenFramebuffersEXT(1, &shadow_fbo);
 		glBindFramebuffer(GL_FRAMEBUFFER_EXT, shadow_fbo);
 		glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT,
-					  GL_COLOR_ATTACHMENT0_EXT,
+					  GL_DEPTH_ATTACHMENT_EXT,
 					  GL_TEXTURE_2D,
 					  shadow_tex,
 					  0);
+
+		first_time = GL_TRUE;
+	}
+
+	glBindFramebuffer(GL_FRAMEBUFFER_EXT, shadow_fbo);
+
+	glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
+	glDrawBuffer(GL_NONE);
+	glReadBuffer(GL_NONE);
+
+	if (first_time) {
+		GLenum status;
+
 		status = glCheckFramebufferStatusEXT (GL_FRAMEBUFFER_EXT);
 		if (status != GL_FRAMEBUFFER_COMPLETE_EXT)
-			fprintf(stderr, "shadow map FBO complete: 0x%08x\n",
+			fprintf(stderr, "shadow map FBO incomplete: 0x%08x\n",
 				status);
 	}
 
-	glDisable(GL_DEPTH_TEST);
-	glBindFramebuffer(GL_FRAMEBUFFER_EXT, shadow_fbo);
 	glViewport(0, 0, shadow_width, shadow_height);
 
 	/* Clear to the material color. */
-	glClearColor(1.0, 0.7, 0.5, 1.0);
-	glClear(GL_COLOR_BUFFER_BIT);
+	glClear(GL_DEPTH_BUFFER_BIT);
 
 	/* Draw the rings in black. */
 	glBindVertexArray(ring.shadow_array_obj);
@@ -155,6 +171,8 @@ generate_rings_shadowmap(void)
 		do_ring_drawelements();
 	}
 
-	glEnable(GL_DEPTH_TEST);
 	glBindFramebuffer(GL_FRAMEBUFFER_EXT, 0);
+	glDrawBuffer(GL_BACK);
+	glReadBuffer(GL_BACK);
+	glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
 }
-- 
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