Merge pull request #38 from Pilzschaf/tutorial42-simplepostprocessing

Simple post processing

Author: Pilzschaf

framebuffer.h

@@ -35,6 +35,10 @@ struct Framebuffer {
         glBindFramebuffer(GL_FRAMEBUFFER, fbo);
     }
 
+    GLuint getTextureId() {
+        return textures[0];
+    }
+
     void unbind() {
         glBindFramebuffer(GL_FRAMEBUFFER, 0);
     }

main.cpp

@@ -88,6 +88,7 @@ int main(int argc, char** argv) {
 
 	Shader fontShader("shaders_old/font.vs", "shaders_old/font.fs");
 	Shader shader("shaders/basic.vs", "shaders/basic.fs");
+	Shader postprocessingShader("shaders_old/postprocess.vs", "shaders_old/postprocess.fs");
 	shader.bind();
 	int directionLocation = GLCALL(glGetUniformLocation(shader.getShaderId(), "u_directional_light.direction"));
 	glm::vec3 sunColor = glm::vec3(0.0f);
@@ -248,6 +249,7 @@ int main(int argc, char** argv) {
 		camera.update();
 
 		framebuffer.bind();
+		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 		shader.bind();
 		model = glm::rotate(model, 1.0f*delta, glm::vec3(0, 1, 0));
 		modelViewProj = camera.getViewProj() * model;
@@ -269,6 +271,14 @@ int main(int argc, char** argv) {
 		shader.unbind();
 		framebuffer.unbind();
 
+		// Postprocessing
+		postprocessingShader.bind();
+		GLCALL(glActiveTexture(GL_TEXTURE0));
+		GLCALL(glBindTexture(GL_TEXTURE_2D, framebuffer.getTextureId()));
+		GLCALL(glUniform1i(glGetUniformLocation(postprocessingShader.getShaderId(), "u_texture"), 0));
+		glDrawArrays(GL_TRIANGLES, 0, 3);
+		postprocessingShader.unbind();
+
 		fontShader.bind();
 
 		int w, h;

shaders_old/postprocess.fs

@@ -0,0 +1,12 @@
+#version 130
+
+varying vec2 v_tex_coords;
+
+uniform sampler2D u_texture;
+
+void main()
+{
+    vec4 color = texture2D(u_texture, v_tex_coords);
+    float average = (color.r + color.g + color.b) / 3.0f;
+    gl_FragColor = vec4(average, average, average, color.a);
+}

shaders_old/postprocess.vs

@@ -0,0 +1,12 @@
+#version 130
+
+varying vec2 v_tex_coords;
+
+void main()
+{
+    float x = -1.0 + float((gl_VertexID & 1) << 2);
+    float y = -1.0 + float((gl_VertexID & 2) << 1);
+    v_tex_coords.x = (x+1.0)*0.5;
+    v_tex_coords.y = (y+1.0)*0.5;
+    gl_Position = vec4(x, y, 0, 1);
+}