Switch triangle for tessellated quad patch with tess shaders

include/InitShader.h

@@ -6,6 +6,7 @@
 GLuint InitShader( const char* computeShaderFile);
 GLuint InitShader( const char* vertexShaderFile, const char* fragmentShaderFile );
 GLuint InitShader( const char* vertexShaderFile, const char* geometryShader, const char* fragmentShaderFile );
+GLuint InitShader( const char* vShaderFile, const char* tcShader, const char* teShader, const char* fShaderFile );
 
 
 #endif

shaders/fragment.glsl

@@ -33,6 +33,8 @@ in VertexData
     vec3 nw;   //world-space normal vector
 } inData;   //block is named 'inData'
 
+in vec3 frag_position;
+
 out vec4 frag_color; //the output color for this fragment    
 
 void main(void)
@@ -56,6 +58,6 @@ void main(void)
     // vec4 specular_term = atten*ks*Ls*pow(max(0.0, dot(rw, vw)), shininess);
 
     // fragcolor = ambient_term + diffuse_term + specular_term;
-    frag_color = vec4(0.45f, 0.82f, 0.52f, 1.0f);
+    frag_color = vec4(frag_position, 1.0f);
 }
 

shaders/tessellation_ctrl.glsl

@@ -0,0 +1,19 @@
+#version 430
+
+layout(vertices = 4) out;  // Define the number of control points per patch (e.g., 4 for a quad)
+
+void main()
+{
+    // Pass through control points to the tessellation evaluation shader
+    gl_out[gl_InvocationID].gl_Position = gl_in[gl_InvocationID].gl_Position;
+
+    // Set the tessellation levels (outer and inner)
+    if (gl_InvocationID == 0) {
+        gl_TessLevelOuter[0] = 5.0; // Level of tessellation along one edge
+        gl_TessLevelOuter[1] = 5.0; // Level of tessellation along another edge
+        gl_TessLevelOuter[2] = 5.0; // Level of tessellation along the other edge
+        gl_TessLevelOuter[3] = 5.0; // Level of tessellation along the other edge
+        gl_TessLevelInner[0] = 5.0; // Level of tessellation for the inner part
+        gl_TessLevelInner[1] = 5.0; // Level of tessellation for the inner part
+    }
+}

shaders/tessellation_eval.glsl

@@ -0,0 +1,17 @@
+#version 430
+
+layout(quads, equal_spacing, ccw) in;  // Define the type of patch (e.g., quads)
+
+out vec3 frag_position;  // Ensure this matches the input in fragment.glsl
+
+void main()
+{
+    // Interpolate the position using the barycentric coordinates from tessellation
+    vec3 pos = mix(mix(gl_in[0].gl_Position.xyz, gl_in[1].gl_Position.xyz, gl_TessCoord.x),
+                   mix(gl_in[3].gl_Position.xyz, gl_in[2].gl_Position.xyz, gl_TessCoord.x),
+                   gl_TessCoord.y);
+    
+    frag_position = pos;
+
+    gl_Position = vec4(pos, 1.0);
+}

shaders/vertex.glsl

@@ -1,30 +1,41 @@
-#version 430            
+#version 430
-layout(location = 0) uniform mat4 M;
-layout(location = 1) uniform float time;
 
-layout(std140, binding = 0) uniform SceneUniforms
+layout(location = 0) in vec3 pos_attrib;
-{
-    mat4 PV;	//camera projection * view matrix
-    vec4 eye_w;	//world-space eye position
-};
-
-layout(location = 0) in vec3 pos_attrib; //this variable holds the position of mesh vertices
 layout(location = 1) in vec2 tex_coord_attrib;
 layout(location = 2) in vec3 normal_attrib;  
 
-out VertexData
+void main() {
-{
+    gl_Position = vec4(pos_attrib, 1.0);
-    vec2 tex_coord;
+}
-    vec3 pw;       //world-space vertex position
-    vec3 nw;   //world-space normal vector
-} outData; 
 
-void main(void)
+
-{
+// #version 400 core 
-    gl_Position = PV*M*vec4(pos_attrib, 1.0); //transform vertices and send result into pipeline
+// layout(location = 0) uniform mat4 M;
+// layout(location = 1) uniform float time;
+
+// layout(std140, binding = 0) uniform SceneUniforms
+// {
+//     mat4 PV;	//camera projection * view matrix
+//     vec4 eye_w;	//world-space eye position
+// };
+
+// layout(location = 0) in vec3 pos_attrib; //this variable holds the position of mesh vertices
+// layout(location = 1) in vec2 tex_coord_attrib;
+// layout(location = 2) in vec3 normal_attrib;  
+
+// out VertexData
+// {
+//     vec2 tex_coord;
+//     vec3 pw;       //world-space vertex position
+//     vec3 nw;   //world-space normal vector
+// } outData; 
+
+// void main(void)
+// {
+//     gl_Position = PV*M*vec4(pos_attrib, 1.0); //transform vertices and send result into pipeline
     
-    //Use dot notation to access members of the interface block
+//     //Use dot notation to access members of the interface block
-    outData.tex_coord = tex_coord_attrib;           //send tex_coord to fragment shader
+//     outData.tex_coord = tex_coord_attrib;           //send tex_coord to fragment shader
-    outData.pw = vec3(M*vec4(pos_attrib, 1.0));		//world-space vertex position
+//     outData.pw = vec3(M*vec4(pos_attrib, 1.0));		//world-space vertex position
-    outData.nw = vec3(M*vec4(normal_attrib, 0.0));	//world-space normal vector
+//     outData.nw = vec3(M*vec4(normal_attrib, 0.0));	//world-space normal vector
-}
+// }

source/InitShader.cpp

@@ -269,3 +269,72 @@ GLuint InitShader(const char* vShaderFile, const char* gShaderFile, const char*
 
    return program;
 }
+
+GLuint InitShader( const char* vShaderFile, const char* tcShader, const char* teShader, const char* fShaderFile )
+{
+   bool error = false;
+   struct Shader 
+   {
+      const char*  filename;
+      GLenum       type;
+      std::string      source;
+   }  shaders[4] = 
+   {
+      { vShaderFile, GL_VERTEX_SHADER, "" },
+      { tcShader, GL_TESS_CONTROL_SHADER, "" },
+      { teShader, GL_TESS_EVALUATION_SHADER, "" },
+      { fShaderFile, GL_FRAGMENT_SHADER, "" }
+   };
+
+   GLuint program = glCreateProgram();
+    
+   for ( int i = 0; i < 4; ++i ) 
+   {
+      Shader& s = shaders[i];
+	   s.source = readShaderSource(s.filename);
+      if ( shaders[i].source.length() == 0 ) 
+      {
+         std::cerr << "Failed to read " << s.filename << std::endl;
+         error = true;
+      }
+
+      GLuint shader = glCreateShader( s.type );
+	  const char *c_str = s.source.c_str();
+	  glShaderSource(shader, 1, (const GLchar**)&c_str, NULL);
+      glCompileShader( shader );
+
+      GLint  compiled;
+      glGetShaderiv( shader, GL_COMPILE_STATUS, &compiled );
+      if ( !compiled ) 
+      {
+         std::cerr << s.filename << " failed to compile:" << std::endl;
+         printShaderCompileError(shader);
+         error = true;
+      }
+
+      glAttachShader( program, shader );
+   }
+
+   /* link  and error check */
+   glLinkProgram(program);
+
+   GLint  linked;
+   glGetProgramiv( program, GL_LINK_STATUS, &linked );
+   if ( !linked ) 
+   {
+      std::cerr << "Shader program failed to link" << std::endl;
+      printProgramLinkError(program);
+
+      error = true;
+   }
+
+   if(error == true)
+   {
+      return -1;
+   }
+
+   /* use program object */
+   glUseProgram(program);
+
+   return program;
+}

source/scene.cpp

@@ -25,6 +25,8 @@
 namespace {
 
 const std::string kVertexShaderPath = "shaders/vertex.glsl";
+const std::string kTessellationCtrlPath = "shaders/tessellation_ctrl.glsl";
+const std::string kTessellationEvalPath = "shaders/tessellation_eval.glsl";
 const std::string kFragmentShaderPath = "shaders/fragment.glsl";
 
 const std::string kQuadVertexPath = "shaders/quad_vertex.glsl";
@@ -57,7 +59,9 @@ Scene::~Scene() {
 void Scene::Init() {
     glewInit();
 
-    glEnable(GL_DEPTH_TEST);
+    // GL_DEPTH_TEST causes artifacts in meshes made up of multiple triangles
+    // disabling for now
+    //glEnable(GL_DEPTH_TEST);
     glEnable(GL_CULL_FACE);
 
     fbo_.Init(window_width, window_height);
@@ -74,21 +78,28 @@ void Scene::Init() {
 
 // Currently creates a test triangle and initializes its buffers
 void Scene::InitBuffers() {
-    GLuint vbo;
+    GLuint patch_vbo;
-    float vertices[] = {
+    // Quad vertices in 3D space
-      -0.5f, -0.5f, 0.0f,
+    float patchVertices[] = {
-       0.5f, -0.5f, 0.0f,
+        -0.5f, -0.5f, 0.0f,  // Bottom-left
-       0.0f,  0.5f, 0.0f
+         0.5f, -0.5f, 0.0f,  // Bottom-right
+         0.5f,  0.5f, 0.0f,   // Top-right
+        -0.5f,  0.5f, 0.0f  // Top-left
+         
     };
 
-    glGenBuffers(1, &vbo);
-    glBindBuffer(GL_ARRAY_BUFFER, vbo);
-    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
-
     glGenVertexArrays(1, &vao_);
+    glGenBuffers(1, &patch_vbo);
     glBindVertexArray(vao_);
-    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
+
+    glBindBuffer(GL_ARRAY_BUFFER, patch_vbo);
+    glBufferData(GL_ARRAY_BUFFER, sizeof(patchVertices), &patchVertices, GL_STATIC_DRAW);
+
+    // Position attribute
     glEnableVertexAttribArray(0);
+    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
+
+    glBindVertexArray(0);
 }
 
 void Scene::InitQuadBuffers() {
@@ -121,7 +132,7 @@ void Scene::InitQuadBuffers() {
 
 // Allows for runtime shader updates
 void Scene::ReloadShader() {
-    GLuint new_shader = InitShader(kVertexShaderPath.c_str(), kFragmentShaderPath.c_str());
+    GLuint new_shader = InitShader(kVertexShaderPath.c_str(), kTessellationCtrlPath.c_str(), kTessellationEvalPath.c_str(), kFragmentShaderPath.c_str());
     if (new_shader == -1) {
         DEBUG_BREAK();
         glClearColor(1.0f, 0.0f, 1.0f, 0.0f);
@@ -141,6 +152,8 @@ void Scene::Display(GLFWwindow* window) {
 
     glUseProgram(shader_program_);
 
+    glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
+
     view_matrix_ = glm::lookAt(glm::vec3(Uniforms::SceneData.eye_w), glm::vec3(0.0f, 0.0f, 0.0f), glm::vec3(0.0f, 1.0f, 0.0f));
     Uniforms::SceneData.PV = projection_matrix_ * view_matrix_; // Projection-View matrix
     Uniforms::BufferSceneData();
@@ -149,7 +162,10 @@ void Scene::Display(GLFWwindow* window) {
     glUniformMatrix4fv(Uniforms::UniformLocs::M, 1, false, glm::value_ptr(model_matrix));
 
     glBindVertexArray(vao_);
-    glDrawArrays(GL_TRIANGLES, 0, 3);
+    glPatchParameteri(GL_PATCH_VERTICES, 4);
+    glDrawArrays(GL_PATCHES, 0, 4);
+
+    glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
 
     fbo_.Unbind();