Using this tutorial https://learnopengl.com/Guest-Articles/2021/Tessellation/Tessellation and this tutorial https://www.youtube.com/watch?v=21gfE-zUym8 I implemented tessellation shaders that I haven't been able to get working after debugging for 8 hours. The error message I get is 
This is what my window is looking like 
This is my tessellation control shader
#version 410 core // specify control points per output per patch // control size of input and output arrays layout(vertices=3) out; // input from vertex shader in vec2 vert_coord[]; // output to evaluation shader out vec2 vertex_coord[]; // for tessellation uniform mat4 view; uniform mat4 model; void main() { // pass attributes through gl_out[gl_InvocationID].gl_Position = gl_in[gl_InvocationID].gl_Position; vertex_coord[gl_InvocationID] = vert_coord[gl_InvocationID]; // control tessellation if(gl_InvocationID==0) { /* dynamic tessellation */ // first: define rendering constants to control tessellation const float MIN_TESS_LEVEL = 4; const float MAX_TESS_LEVEL = 64; const float MIN_DISTANCE = 20; const float MAX_DISTANCE = 800; // second: transform each vertex into each eye vec4 eye_space_pos_1 = view * model * gl_in[0].gl_Position; vec4 eye_space_pos_2 = view * model * gl_in[1].gl_Position; vec4 eye_space_pos_3 = view * model * gl_in[2].gl_Position; // third: distance from camera scaled between 0 and 1 float distance_1 = clamp((abs(eye_space_pos_1.z)-MIN_DISTANCE)/(MAX_DISTANCE-MIN_DISTANCE), 0.0, 1.0); float distance_2 = clamp((abs(eye_space_pos_2.z)-MIN_DISTANCE)/(MAX_DISTANCE-MIN_DISTANCE), 0.0, 1.0); float distance_3 = clamp((abs(eye_space_pos_3.z)-MIN_DISTANCE)/(MAX_DISTANCE-MIN_DISTANCE), 0.0, 1.0); // fourth: interpolate edge tessellation level based on closer vertex float tess_level_1 = mix(MAX_TESS_LEVEL, MIN_TESS_LEVEL, min(distance_3, distance_1)); float tess_level_2 = mix(MAX_TESS_LEVEL, MIN_TESS_LEVEL, min(distance_1, distance_2)); float tess_level_3 = mix(MAX_TESS_LEVEL, MIN_TESS_LEVEL, min(distance_2, distance_3)); // fifth: set the corresponding outer tessellation levels gl_TessLevelOuter[0] = tess_level_1; gl_TessLevelOuter[1] = tess_level_2; gl_TessLevelOuter[2] = tess_level_3; // sixth: set the inner tessellation levels gl_TessLevelInner[0] = max(tess_level_1, tess_level_3); gl_TessLevelInner[1] = max(tess_level_1, tess_level_2); } } This is the tessellation evaluation shader
#version 410 core // from control shader layout(triangles, equal_spacing, ccw) in; // input from control shader in vec2 vertex_coord[]; // output vec out vec2 vert; // allows for object transformations and for movement uniform mat4 model; uniform mat4 view; uniform mat4 projection; void main() { // patch coords float u = gl_TessCoord.x; float v = gl_TessCoord.y; float w = gl_TessCoord.z; // barycentric interpolation vec2 tex_coord = u * vertex_coord[0] + v * vertex_coord[1] + w * vertex_coord[2]; // get control coords vec4 pos_1 = gl_in[0].gl_Position; vec4 pos_2 = gl_in[1].gl_Position; vec4 pos_3 = gl_in[2].gl_Position; // more barycentric interpolation vec4 pos = u * pos_1 + v * pos_2 + w * pos_3; // position gl_Position = model * view * projection * pos; vert = tex_coord; } This is the vertex shader
#version 410 core // position of the object layout (location = 0) in vec3 pos; layout (location = 1) in vec2 vert; out vec2 vert_coord; void main() { // position object gl_Position = vec4(pos, 1.0f); vert_coord = vert; } This is the fragment shader
#version 410 core out vec4 color; void main() { color = vec4(0.86f, 0.74f, 0.09f, 1.0f); } This is the shader loader for the tessellation shaders
// tess control tessellation_control_shader = glCreateShader(GL_TESS_CONTROL_SHADER); glShaderSource(tessellation_control_shader, 1, &tessellation_control_shader_text, NULL); glCompileShader(tessellation_control_shader); glGetShaderiv(tessellation_control_shader, GL_COMPILE_STATUS, &success); if(!success) { glGetShaderInfoLog(tessellation_control_shader, 512, NULL, info_log); printf("Tessellation control shader failed: %s\n", info_log); perror(info_log); } // tess eval tessellation_evaluation_shader = glCreateShader(GL_TESS_EVALUATION_SHADER); glShaderSource(tessellation_evaluation_shader, 1, &tessellation_evaluation_shader_text, NULL); glCompileShader(tessellation_evaluation_shader); glGetShaderiv(tessellation_evaluation_shader, GL_COMPILE_STATUS, &success); if(!success) { glGetShaderInfoLog(tessellation_evaluation_shader, 512, NULL, info_log); printf("Tessellation evaluation shader failed: %s\n", info_log); perror(info_log); } This is the tessellation initialization, vertices, indices and, buffers
#define NUM_PATCH_PTS 3 // shader loading unsigned int shader_program = load_shaders("vert.glsl", "frag.glsl", "tes_ctrl.glsl", "tes_eval.glsl"); // octahedron, vertices provided by https://gamedev.stackexchange.com/users/39518/dmgregory unsigned int draw_calls = 48; float vertices[] = { //top-north-east 0.0, 1.0, 0.0, 0.0, 0.0, 1.0, 1.0, 0.0, 0.0, //top-north-west 0.0, 1.0, 0.0, -1.0, 0.0, 0.0, 0.0, 0.0, 1.0, //top-south-west 0.0, 1.0, 0.0, 0.0, 0.0, -1.0, -1.0, 0.0, 0.0, //top-south-east 0.0, 1.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, -1.0, //bottom-north-east 0.0, -1.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, //bottom-north-west 0.0, -1.0, 0.0, 0.0, 0.0, 1.0, -1.0, 0.0, 0.0, //bottom-south-west 0.0, -1.0, 0.0, -1.0, 0.0, 0.0, 0.0, 0.0, -1.0, //bottom-south-east 0.0, -1.0, 0.0, 0.0, 0.0, -1.0, 1.0, 0.0, 0.0, }; unsigned int indices[] = { // first triangle 0, 1, 2, // second triangle 3, 4, 5, // third triangle 6, 7, 8, // fourth triangle 9, 10, 11, // fifth triangle 12, 13, 14, // sixth triangle 15, 16, 17, // seventh triangle 18, 19, 20, // eighth triangle 21, 22, 23 }; unsigned int vbo, vao, ebo; glGenVertexArrays(1, &vao); glGenBuffers(1, &vbo); glGenBuffers(1, &ebo); glBindVertexArray(vao); // upload vertex data to gpu glBindBuffer(GL_ARRAY_BUFFER, vbo); glBufferData(GL_ARRAY_BUFFER, sizeof(vertices) * sizeof(double), &vertices[0], GL_STATIC_DRAW); // upload index data to gpu glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo); glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices) * sizeof(unsigned int), &indices[0], GL_STATIC_DRAW); // position attribute glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0); glEnableVertexAttribArray(0); // max tessellation points / patches glPatchParameteri(GL_PATCH_VERTICES, NUM_PATCH_PTS); This is the draw call
glBindVertexArray(vao); glDrawArrays(GL_PATCHES, 0, draw_calls*draw_calls*NUM_PATCH_PTS); 
