openglopengl-esopengl-3blending
OpenGL Render to a texture
How can I render to a texture using framebuffer objects and use that texture as an input for my shader.
I need to perform this for programmable blending.
I am able to create a FBO and texture individually but not able to render to that texture and attach my frame buffer object.
I need to render to texture because I want to pass this texture to my shader so that I am able to write my own programmable blending equation.
#include <glad/glad.h>
#include <GLFW\glfw3.h>
#include <iostream>
#include "shader.h"
#include "std_image.h"
using namespace std;
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
glViewport(0, 0, width, height);
}
int main()
{
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
GLFWwindow* window = glfwCreateWindow(800, 600, "LearnOpenGL", NULL, NULL);
if (window == NULL)
{
cout << "Failed to create GLFW window" <<endl;
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
{
cout << "Failed to initialize GLAD" <<endl;
return -1;
}
glViewport(0, 0, 800, 600);
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
///////////////////////////////////////////////////////////////////////////////////
Shader ourShader("Shader.vs", "Shader.fs");
Shader ourShader2("Shader.vs", "Shader2.fs");
unsigned int FBO;
glGenFramebuffers(1, &FBO);
glBindFramebuffer(GL_FRAMEBUFFER, FBO);
unsigned int attachment_index_color_texture = 0;
glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0 + attachment_index_color_texture, GL_UNSIGNED_BYTE, 0);
glBindFramebuffer(GL_FRAMEBUFFER, 0); //unbind framebuffer
float vertices[] = {
// positions // colors // texture coords
0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, // top right
0.5f, -0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, // bottom right
-0.5f, -0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, // bottom left
-0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 1.0f // top left
};
unsigned int indices[] = {
0, 1, 3, // first triangle
1, 2, 3 // second triangle
};
float vertices2[] = {
// positions // colors // texture coords
0.75f, 0.75f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f, // top right
0.75f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, // bottom right
0.0f, 0.0f, 0.0f, 0.0f,1.0f, 0.0f, 0.0f, 0.0f, // bottom left
0.0f, 0.75f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f // top left
};
unsigned int indices2[] = {
0, 1, 2, // first triangle
0, 2, 3 // second triangle
};
unsigned int VBO[2],VAO[2],EBO[2];
glGenVertexArrays(2, VAO);
glGenBuffers(2, VBO);
glGenBuffers(2, EBO);
glBindVertexArray(VAO[0]);
glBindBuffer(GL_ARRAY_BUFFER, VBO[0]);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[0]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
glEnableVertexAttribArray(1);
glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
glEnableVertexAttribArray(2);
glBindVertexArray(0);
glBindVertexArray(VAO[1]);
glBindBuffer(GL_ARRAY_BUFFER, VBO[1]);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices2), vertices2, GL_STATIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[1]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices2), indices2, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
glEnableVertexAttribArray(1);
glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
glEnableVertexAttribArray(2);
glEnable(GL_BLEND);
glBlendFunc(GL_ONE, GL_ONE);
while (!glfwWindowShouldClose(window))
{
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
ourShader.use();
glBindVertexArray(VAO[0]);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
ourShader2.use();
glBindVertexArray(VAO[1]);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
glfwSwapBuffers(window);
glfwPollEvents();
}
/*glDeleteVertexArrays(1, &VAO);
glDeleteBuffers(1, &VBO);
glDeleteBuffers(1, &EBO);*/
glfwTerminate();
return 0;
}
Edit 1:
I am now attaching my texture to fbo, also rendering on my textrue as shown below:
while (!glfwWindowShouldClose(window))
{
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
ourShader.use();
glBindVertexArray(VAO[0]);
unsigned int FBO, color, depth;
glGenFramebuffers(1, &FBO);
glGenTextures(1, &color);
glBindFramebuffer(GL_FRAMEBUFFER, FBO);
glBindTexture(GL_TEXTURE_2D, color);
glGenRenderbuffers(1, &depth);
glTexImage2D(GL_TEXTURE_2D,
0,
GL_RGBA,
800, 600,
0,
GL_RGBA,
GL_UNSIGNED_BYTE,
NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, color, 0);
GLenum DrawBuffers[1] = { GL_COLOR_ATTACHMENT0 };
glDrawBuffers(1, DrawBuffers); // "1" is the size of DrawBuffers
if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
return false;
glBindFramebuffer(GL_FRAMEBUFFER, FBO);
glViewport(0, 0, 800, 600); // Render on the whole framebuffer, complete from the lower left corner to the upper right
glBindFramebuffer(GL_FRAMEBUFFER, 0);
ourShader2.use();
glBindVertexArray(VAO[1]);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
glfwSwapBuffers(window);
glfwPollEvents();
}
One issue left is how can i pass my texture "color" in my shader.
Thanks for help
Edit2:
I am attaching my whole code, can u please check why i am not getting anything on screen.
main.cpp:
#include <glad/glad.h>
#include <GLFW\glfw3.h>
#include <iostream>
#include "shader.h"
#include "std_image.h"
using namespace std;
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
glViewport(0, 0, width, height);
}
int main()
{
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
GLFWwindow* window = glfwCreateWindow(800, 600, "LearnOpenGL", NULL, NULL);
if (window == NULL)
{
cout << "Failed to create GLFW window" <<endl;
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
{
cout << "Failed to initialize GLAD" <<endl;
return -1;
}
glViewport(0, 0, 800, 600);
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
///////////////////////////////////////////////////////////////////////////////////
Shader ourShader("Shader.vs", "Shader.fs");
Shader ourShader2("Shader.vs", "Shader2.fs");
//glBindFramebuffer(GL_FRAMEBUFFER, 0); //unbind framebuffer
float vertices[] = {
// positions // colors // texture coords
0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, // top right
0.5f, -0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, // bottom right
-0.5f, -0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, // bottom left
-0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 1.0f // top left
};
unsigned int indices[] = {
0, 1, 3, // first triangle
1, 2, 3 // second triangle
};
float vertices2[] = {
// positions // colors // texture coords
0.75f, 0.75f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f, // top right
0.75f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, // bottom right
0.0f, 0.0f, 0.0f, 0.0f,1.0f, 0.0f, 0.0f, 0.0f, // bottom left
0.0f, 0.75f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f // top left
};
unsigned int indices2[] = {
0, 1, 2, // first triangle
0, 2, 3 // second triangle
};
unsigned int VBO[2],VAO[2],EBO[2];
glGenVertexArrays(2, VAO);
glGenBuffers(2, VBO);
glGenBuffers(2, EBO);
glBindVertexArray(VAO[0]);
glBindBuffer(GL_ARRAY_BUFFER, VBO[0]);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[0]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
glEnableVertexAttribArray(1);
glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
glEnableVertexAttribArray(2);
glBindVertexArray(0);
glBindVertexArray(VAO[1]);
glBindBuffer(GL_ARRAY_BUFFER, VBO[1]);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices2), vertices2, GL_STATIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[1]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices2), indices2, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
glEnableVertexAttribArray(1);
glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
glEnableVertexAttribArray(2);
glEnable(GL_BLEND);
glBlendFunc(GL_ONE, GL_ONE);
while (!glfwWindowShouldClose(window))
{
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
ourShader.use();
glBindVertexArray(VAO[0]);
unsigned int FBO, color, depth;
glGenFramebuffers(1, &FBO);
glGenTextures(1, &color);
glBindFramebuffer(GL_FRAMEBUFFER, FBO);
glBindTexture(GL_TEXTURE_2D, color);
glGenRenderbuffers(1, &depth);
glTexImage2D(GL_TEXTURE_2D,
0,
GL_RGBA,
800, 600,
0,
GL_RGBA,
GL_UNSIGNED_BYTE,
NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, color, 0);
unsigned int decalTexLocation;
decalTexLocation = glGetUniformLocation(ourShader.ID, "DecalTex");
glUniform1i(decalTexLocation, 0);
glActiveTexture(GL_TEXTURE0 + 0);
glBindTexture(GL_TEXTURE_2D, color);
GLenum DrawBuffers[2] = { GL_COLOR_ATTACHMENT0 };
glDrawBuffers(1, &DrawBuffers[0]); // "1" is the size of DrawBuffers
if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
return false;
glViewport(0, 0, 800, 600); // Render on the whole framebuffer, complete from the lower left corner to the upper right
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
ourShader2.use();
glBindVertexArray(VAO[1]);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
glfwSwapBuffers(window);
glfwPollEvents();
}
/*glDeleteVertexArrays(1, &VAO);
glDeleteBuffers(1, &VBO);
glDeleteBuffers(1, &EBO);*/
glfwTerminate();
return 0;
}
Fragment Shader1:
#version 330 core
out vec4 FragColor;
in vec3 ourColor;
void main()
{
// vec4 dst = getCurrentColorAtOutputFragmentPosition();
FragColor = vec4(ourColor, 1.0);
}
Fragment Shader2:
#version 330 core
out vec4 FragColor;
uniform sampler2D DecalTex;
in vec3 ourColor;
void main()
{
vec2 coords = gl_TexCoord[0].xy;
vec3 normalColor = texture2D(DecalTex, coords).rgb; //original color
FragColor = vec4(normalColor.x,normalColor.y,normalColor.z, 1.0);
}
Vertex Shader:
#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aColor;
layout (location = 2) in vec2 aTexCoord;
out vec3 ourColor;
out vec2 TexCoord;
void main()
{
gl_Position = vec4(aPos, 1.0);
ourColor = aColor;
TexCoord = aTexCoord;
}
Edit 3:
Int the below code i am rendering 2 rectangles, one of a texture using FBO(Frame Buffer Object) and second on screen.
I am able to render both on screen.
I have written 2 fragment shader and 2 vertex shader.
One pair of fragment and vertex shader is use for rendering on texture and other is used for rendering on screen.
My main file:
#include <glad/glad.h>
#include <GLFW\glfw3.h>
#include <iostream>
#include "shader.h"
#include "std_image.h"
using namespace std;
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
glViewport(0, 0, width, height);
}
int main()
{
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
GLFWwindow* window = glfwCreateWindow(800, 600, "LearnOpenGL", NULL, NULL);
if (window == NULL)
{
cout << "Failed to create GLFW window" <<endl;
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
{
cout << "Failed to initialize GLAD" <<endl;
return -1;
}
glViewport(0, 0, 800, 600);
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
///////////////////////////////////////////////////////////////////////////////////
Shader ourShader("Shader.vs", "Shader.fs");
Shader ourShader2("Shader2.vs", "Shader2.fs");
//glBindFramebuffer(GL_FRAMEBUFFER, 0); //unbind framebuffer
float vertices[] = {
// positions // colors // texture coords
0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, // top right
0.5f, -0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, // bottom right
-0.5f, -0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, // bottom left
-0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 1.0f // top left
};
unsigned int indices[] = {
0, 1, 3, // first triangle
1, 2, 3 // second triangle
};
float vertices2[] = {
// positions // colors // texture coords
1.0, 1.0, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f, // top right
1.0, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, // bottom right
0.0f, 0.0f, 0.0f, 0.0f,1.0f, 0.0f, 0.0f, 0.0f, // bottom left
0.0f, 1.0, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f // top left
};
unsigned int indices2[] = {
0, 1, 2, // first triangle
0, 2, 3 // second triangle
};
unsigned int VBO[2],VAO[2],EBO[2];
glGenVertexArrays(2, VAO);
glGenBuffers(2, VBO);
glGenBuffers(2, EBO);
glBindVertexArray(VAO[0]);
glBindBuffer(GL_ARRAY_BUFFER, VBO[0]);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[0]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
glEnableVertexAttribArray(1);
glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
glEnableVertexAttribArray(2);
glBindVertexArray(0);
glBindVertexArray(VAO[1]);
glBindBuffer(GL_ARRAY_BUFFER, VBO[1]);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices2), vertices2, GL_STATIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[1]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices2), indices2, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
glEnableVertexAttribArray(1);
glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
glEnableVertexAttribArray(2);
/*glEnable(GL_BLEND);
glBlendFunc(GL_ONE, GL_ONE)*/;
unsigned int color;
glGenTextures(1, &color);
glBindTexture(GL_TEXTURE_2D, color);
glTexImage2D(GL_TEXTURE_2D,
0,
GL_RGBA,
800, 600,
0,
GL_RGBA,
GL_UNSIGNED_BYTE,
NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
unsigned int FBO;
glGenFramebuffers(1, &FBO);
glBindFramebuffer(GL_FRAMEBUFFER, FBO);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, color, 0);
while (!glfwWindowShouldClose(window))
{
ourShader.use();
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glBindVertexArray(VAO[0]);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
ourShader2.use();
int texturehandle = glGetUniformLocation(ourShader.ID, "DecalTex");
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, color);
glUniform1i(texturehandle, 0);
glBindVertexArray(VAO[1]);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwTerminate();
return 0;
}
Veretx Shader 1:
#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aColor;
layout (location = 2) in vec2 aTexCoord;
out vec3 ourColor;
out vec2 TexCoord;
void main()
{
gl_Position = vec4(aPos, 1.0);
ourColor = aColor;
TexCoord = aTexCoord;
}
Fragment Shader 1
#version 330 core
out vec4 FragColor;
in vec3 ourColor;
void main()
{
// vec4 dst = getCurrentColorAtOutputFragmentPosition();
FragColor = vec4(ourColor, 1.0);
}
Vertex Shader 2
#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aColor;
layout (location = 2) in vec2 aTexCoord;
out vec3 ourColor;
out vec2 myUV;
void main()
{
gl_Position = vec4(aPos, 1.0);
ourColor = aColor;
myUV = vec2(aPos.x,aPos.y);
}
Fragment Shader 2
#version 330 core
out vec4 FragColor;
uniform sampler2D DecalTex;
in vec3 ourColor;
in vec2 UV;
void main()
{
vec2 outUV = vec2(0.26,0.26);
vec4 myFragColor = texture2D(DecalTex,outUV);
//vec4 myFragColor = texture2D(DecalTex,UV);
//FragColor = vec4(ourColor,1.0);
vec4 tempFragColor = vec4(ourColor, 1.0);
//FragColor = myFragColor;
FragColor = myFragColor + tempFragColor;
//FragColor = (1.0,1.0,1.0,1.0);//tempFragColor;
}
Here the issue is that when i use the line:
vec4 myFragColor = texture2D(DecalTex,UV);
I am not able to get any value in myFragColor, as a result normal rendering occurs.
but if i change to
vec2 outUV = vec2(0.26,0.26);
vec4 myFragColor = texture2D(DecalTex,outUV);
I am able to get value of destination pixel and hence rending is done according to my need.
Can u please tell why i am not able from:
vec4 myFragColor = texture2D(DecalTex,UV);
Edit 4
Now i am able to access my destination pixel, but only 1 issue is left:
first rectangles co-ordinates (-0.5,-0.5) <-----> (0.5,0.5)
Second Rectangles co - ordinates (0,0) <----> (1,1)
Area of intersection (0,0) <----> (0.5,0.5) --------> This should be yellow (Red + Green)
But area (0.26,0.26) <-------> (0.74,0.74) ------> this is comming out yellow, very strange any reason..?
Latest Fragment Shader:
#version 330 core
out vec4 FragColor;
uniform sampler2D DecalTex;
in vec3 ourColor;
in vec2 myUV;
void main()
{
vec4 myFragColor = texture2D(DecalTex,myUV);
FragColor = vec4(ourColor,1.0);
vec4 tempFragColor = vec4(ourColor, 1.0);
FragColor = myFragColor + tempFragColor;
}
Expected Result:
Solution
When you compile Fragment Shader 2, then you get an error message like this (dependent on the graphics driver);
0(12) : error C7616: global variable
gl_TexCoordis removed after version 140
This means you can't use gl_TexCoord in combination with #version 330 core.
You already have defined a varying out variable for the texture coordinates in the vertex shader.
out vec2 myUV;
Define the corresponding in variable in the fragment shader and use it, instead of gl_TexCoord:
#version 330 core
out vec4 FragColor;
uniform sampler2D DecalTex;
in vec3 ourColor;
in vec2 myUV;
void main()
{
vec4 myFragColor = texture2D(DecalTex,myUV);
FragColor = myFragColor;
}
Extension to the answer:
To link the shader program correctly and make it proper work, the names of the varying out variables have to perfectly match to the names of the varying in variables.
This means this the output variable for the texture coordinates in named myUV, in the vertex shader:
out vec2 myUV;
The corresponding input variable in the fragment shader has to be named myUV, too:
in vec2 myUV;
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- GLSL Rounded Rectangle Corners Are Stretched
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- Creating an OpenGL context using SDL2 on macOS
- Difference between C++ and OpenGL objects
- unity3d, multiple render targets - different behavior in Direct3D/OpenGl
- For instanced draw calls, does the vertex count make a difference to performance?
- Assistance in Debug OpenGL glsl Shader or Code using it
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- Sending GL Uniforms: Multiple floats vs packing into vector
- Using Depth FBO for shadow map causes weird behaviour