纹理不适合正方形-OpenGL [英] Texture does not fit in the square - OpenGL
问题描述
我正在尝试创建一个正方形并将红色圆圈置于其中.如您所见，在简单的版本I中，我将(-1，1)范围映射到(0,1)范围:
I am trying to create a square and put a red circle middle of it. As you can see in the simple vert I map (-1, 1) range to (0,1) range:
coord = position.xy*0.5 + vec2(0.5,0.5);
如果您查看simple.frag，则显示以下行:
If you look at the simple.frag, there is this line:
if(abs(length(coord - vec2(0.5,0.5))) < 0.3)
因此，我期望方形的中间有一个红色的圆圈.但这会发生:
Thus I am expecting red circle at the middle of square. However this happens:
圆心超出(0.5，0.5).如果我将该行更改为此:
The center of circle is beyond of (0.5, 0.5). If I change that line to this:
if(abs(length(coord - vec2(0.0,0.0))) < 0.3)
输出为:
圆的中心位于预期的左下角.但是不应该在右上角(1,1)吗?另外这个圆也不是完美的圆.我想念什么?
The center of the circle is at the bottom-left corner as expected. However shouldn't be the top right corner (1,1)? Also the circle is not perfect circle. What am I missing?
初始化:
Shader simpleShader("simple.vert", "simple.frag");
Shader quadShader("quad.vert", "quad.frag");
GLfloat inVertices[] = {
-1.0f, 1.0f, 0.0,
-1.0f, -1.0f, 0.0,
1.0f, -1.0f, 0.0,
-1.0f, 1.0f, 0.0,
1.0f, -1.0f, 0.0,
1.0f, 1.0f, 0.0 };
GLfloat quadVertices[] = {
-1.0f, 1.0f, 0.0f, 0.0f, 1.0f,
-1.0f, -1.0f, 0.0f, 0.0f, 0.0f,
1.0f, -1.0f, 0.0f, 1.0f, 0.0f,
-1.0f, 1.0f, 0.0f, 0.0f, 1.0f,
1.0f, -1.0f, 0.0f, 1.0f, 0.0f,
1.0f, 1.0f, 0.0f, 1.0f, 1.0f
};
GLuint inVAO, inVBO;
glGenVertexArrays(1, &inVAO);
glGenBuffers(1, &inVBO);
glBindVertexArray(inVAO);
glBindBuffer(GL_ARRAY_BUFFER, inVBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(inVertices), &inVertices, GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (GLvoid*)0);
glBindVertexArray(0);
GLuint quadVAO, quadVBO;
glGenVertexArrays(1, &quadVAO);
glGenBuffers(1, &quadVBO);
glBindVertexArray(quadVAO);
glBindBuffer(GL_ARRAY_BUFFER, quadVBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(quadVertices), &quadVertices, GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (GLvoid*)0);
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (GLvoid*)(3 * sizeof(GLfloat)));
glBindVertexArray(0);
GLuint textureColorbuffer;
glGenTextures(1, &textureColorbuffer);
glBindTexture(GL_TEXTURE_2D, textureColorbuffer);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 256, 256, 0, GL_RGB, GL_UNSIGNED_BYTE, NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glBindTexture(GL_TEXTURE_2D, 0);
GLuint framebuffer;
glGenFramebuffers(1, &framebuffer);
glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
// Create a color attachment texture
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, textureColorbuffer, 0);
if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
std::cout << "ERROR::FRAMEBUFFER:: Framebuffer is not complete!" << std::endl;
glBindFramebuffer(GL_FRAMEBUFFER, 0);
主循环；
glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
// Draw our first triangle
simpleShader.Use();
glBindVertexArray(inVAO);
glDrawArrays(GL_TRIANGLES, 0, 6);
glBindVertexArray(0);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
quadShader.Use();
modelLoc = glGetUniformLocation(quadShader.Program, "model");
viewLoc = glGetUniformLocation(quadShader.Program, "view");
projLoc = glGetUniformLocation(quadShader.Program, "projection");
glUniformMatrix4fv(modelLoc, 1, GL_FALSE, glm::value_ptr(model));
glUniformMatrix4fv(viewLoc, 1, GL_FALSE, glm::value_ptr(view));
glUniformMatrix4fv(projLoc, 1, GL_FALSE, glm::value_ptr(projection));
glBindVertexArray(quadVAO);
glBindTexture(GL_TEXTURE_2D, textureColorbuffer); // Use the color attachment texture as the texture of the quad plane
glDrawArrays(GL_TRIANGLES, 0, 6);
glBindVertexArray(0);
// Swap the screen buffers
glfwSwapBuffers(window);
simple.vert:
simple.vert:
#version 330 core
layout (location = 0) in vec3 position;
out vec2 coord;
void main(){
coord = position.xy*0.5 + vec2(0.5,0.5);
gl_Position = vec4(position, 1.0f);
}
simple.frag:
simple.frag:
#version 330 core
in vec2 coord;
out vec4 color;
void main(){
if(abs(length(coord - vec2(0.5,0.5))) < 0.3)
color = vec4(1.0f, 0.0f, 0.0f, 1.0f);
else
color = vec4(0.0f, 1.0f, 0.0f, 1.0f);
}
quad.vert:
quad.vert:
#version 330 core
layout (location = 0) in vec3 position;
layout (location = 1) in vec2 texCoords;
uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;
out vec2 TexCoords;
void main()
{
gl_Position = projection * view * model * vec4(position, 1.0f);
TexCoords = texCoords;
}
quad.frag:
quad.frag:
#version 330 core
in vec2 TexCoords;
out vec4 color;
uniform sampler2D screenTexture;
void main()
{
color = texture(screenTexture, TexCoords);
}
推荐答案
在绘制到纹理时必须修改视口.如果使用窗口的视口，则OpenGL假定纹理的大小与窗口相同.因此，只有整个图像的左下角会出现在纹理中.
You have to modify your viewport when drawing to the texture. If you use the viewport of the window, OpenGL assumes that the texture has the same size as the window. Therefore, only the lower left corner of the entire image will end up in the texture.
因此，在渲染到纹理之前:
So before rendering to the texture:
glViewport(0, 0, 256, 256);
...并在绘制最终场景之前将其还原.
... and revert that before drawing the final scene.
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