I am confused as to why the compute shader is implicitly adding color to untouched pixels of an image2D variable. This holds true if I shade (100+)^2 pixels white, and shade the [0,0] pixel as black; the result is a window where all pixels of the window are grey.
This is an issue because I cannot make any pixel art; they all blend for some reason.
i.e. I am doing pixel blending art, not pixel perfect art; and it’s a mess!
Why is life this way?
CODE
*Compute Shader*
#version 430 core
layout (binding = 0, rgba32f) uniform image2D img;
layout (local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
void main(void) {
vec4 color;
if (gl_GlobalInvocationID.xy == ivec2(0,0)){
color = vec4(0.0,0.0,0.0,1.0);
}
else {
color = vec4(1.0,1.0,1.0,1.0);
}
ivec2 pos = ivec2(gl_GlobalInvocationID.xy);
imageStore(img, pos, color);
}
*Vertex Shader*
#version 430 core
layout (location = 0) in vec3 vPos;
layout (location = 1) in vec2 tPos1;
out vec2 tPos2;
void main(){
gl_Position = vec4(vPos, 1.0);
tPos2 = tPos1;
}
*Fragment Shader*
#version 430 core
uniform sampler2D img;
in vec2 tPos2;
out vec4 FragColor;
void main()
{
FragColor = texture(img, tPos2);
}
*Suspective App Code*
#include <GLAD/glad.h>
#include <GLFW/glfw3.h>
#include "Shader.h"
int main(void) {
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_ANY_PROFILE, GLFW_OPENGL_CORE_PROFILE);
glfwWindowHint(GLFW_DECORATED, false);
GLFWwindow* window = glfwCreateWindow(1200, 800, "(PC)", NULL, NULL);
const GLFWvidmode* mode = glfwGetVideoMode(glfwGetPrimaryMonitor());
int windowX, windowY;
glfwSetWindowSize(window, mode->width/2, mode->height/2);
glfwGetWindowSize(window, &windowX, &windowY);
glfwSetWindowPos(window, (mode->width - windowX)/2, (mode->height - windowY)/2);
glfwMakeContextCurrent(window);
glViewport(0, 0, windowX, windowY);
// Data
float data[] = {
// x-y-z positions, & u-v texCoordinates (in a Row->)
-1.0,-1.0, 0.0, 0.0,0.0,
-1.0, 1.0, 0.0, 0.0,1.0,
1.0, 1.0, 0.0, 1.0,1.0,
-1.0,-1.0, 0.0, 0.0,0.0,
1.0,-1.0, 0.0, 1.0,0.0,
1.0, 1.0, 0.0, 1.0,1.0
};
// Compute Shader
Shader computeShader("shader.compute");
computeShader.Use();
glActiveTexture(GL_TEXTURE0);
GLuint computeTexture;
glGenTextures(1, &computeTexture);
glBindTexture(GL_TEXTURE_2D, computeTexture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
// If I remove the above 2 lines, it will not display anything...
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA32F, windowX, windowY, 0, GL_RGBA, GL_FLOAT, 0);
glBindImageTexture(0, computeTexture, 0, GL_FALSE, 0, GL_WRITE_ONLY, GL_RGBA32F);
// Vertex & Fragment Shader
Shader vertexfragmentShader("shader.vs", "shader.fs");
vertexfragmentShader.Use();
// VAO
GLuint vao;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
// VBO
GLuint vbo;
glGenBuffers(1, &vbo);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(data), data, GL_STATIC_DRAW);
// Data Lx Configuration
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)3);
glEnableVertexAttribArray(1);
// Texture
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, computeTexture);
glClearColor(0.1,0.1,0.1,1.0);
glDisable(GL_DEPTH_TEST);
while (!glfwWindowShouldClose(window)) {
computeShader.Use();
glDispatchCompute((GLuint)windowX, (GLuint)windowY, 1);
glClear(GL_COLOR_BUFFER_BIT);
vertexfragmentShader.Use();
glBindVertexArray(vao);
glDrawArrays(GL_TRIANGLES, 0, 6);
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwTerminate();
return 1;
}
If I run all code in this current state (including the parts I left out that are correct), it outputs grey, because the [0,0] pixel was set to black, and everything else was set to white.
