显示正交的OpenGL投影矩阵

Question

我使用了正交摄影机，但是我想尝试实现透视摄影机，以便稍后可以进行一些视差效果。尝试实施时遇到一些问题。深度似乎无法正常工作。我沿x轴旋转2d图像，以模拟其稍微放下，因此我看到投影矩阵正在工作。不过，它仍显示为正交视图。

这是我的一些代码：

CameraPersp::CameraPersp() :
    _camPos(0.0f,0.0f,0.0f), _modelMatrix(1.0f), _viewMatrix(1.0f), _projectionMatrix(1.0f)

调用init的函数来设置矩阵变量：

void CameraPersp::init(int screenWidth, int screenHeight)
{
    _screenHeight = screenHeight;
    _screenWidth = screenWidth;

    _modelMatrix = glm::translate(_modelMatrix, glm::vec3(0.0f, 0.0f, 0.0f));
    _modelMatrix = glm::rotate(_modelMatrix, glm::radians(-55.0f), glm::vec3(1.0f, 0.0f, 0.0f));
    _viewMatrix = glm::translate(_viewMatrix, glm::vec3(0.0f, 0.0f, -3.0f));
    _projectionMatrix = glm::perspective(glm::radians(45.0f), static_cast<float>(_screenWidth) / _screenHeight, 0.1f, 100.0f);
}

初始化要使用x，y，z，width，height，src加载的纹理

_sprites.back()->init(-0.5f, -0.5f, 0.0f, 1.0f, 1.0f, "src/content/sprites/DungeonCrawlStoneSoupFull/monster/deep_elf_death_mage.png");

将矩阵发送到vertexShader：

    GLint mLocation = _colorProgram.getUniformLocation("M");
    glm::mat4 mMatrix = _camera.getMMatrix();
    //glUniformMatrix4fv(mLocation, 1, GL_FALSE, &(mMatrix[0][0]));
    glUniformMatrix4fv(mLocation, 1, GL_FALSE, glm::value_ptr(mMatrix));

    GLint vLocation = _colorProgram.getUniformLocation("V");
    glm::mat4 vMatrix = _camera.getVMatrix();
    //glUniformMatrix4fv(vLocation, 1, GL_FALSE, &(vMatrix[0][0]));
    glUniformMatrix4fv(vLocation, 1, GL_FALSE, glm::value_ptr(vMatrix));

    GLint pLocation = _colorProgram.getUniformLocation("P");
    glm::mat4 pMatrix = _camera.getPMatrix();
    //glUniformMatrix4fv(pLocation, 1, GL_FALSE, &(pMatrix[0][0]));
    glUniformMatrix4fv(pLocation, 1, GL_FALSE, glm::value_ptr(pMatrix));

这是我的顶点着色器：

#version 460
//The vertex shader operates on each vertex

//input data from VBO. Each vertex is 2 floats
in vec3 vertexPosition;
in vec4 vertexColor;
in vec2 vertexUV;

out vec3 fragPosition;
out vec4 fragColor;
out vec2 fragUV;

//uniform mat4 MVP;
uniform mat4 M;
uniform mat4 V;
uniform mat4 P;

void main() {
    //Set the x,y position on the screen
    //gl_Position.xy = vertexPosition;
    gl_Position = M * V * P * vec4(vertexPosition, 1.0);

    //the z position is zero since we are 2d
    //gl_Position.z = 0.0;

    //indicate that the coordinates are nomalized
    gl_Position.w = 1.0;

   fragPosition = vertexPosition;
   fragColor = vertexColor;
   // opengl needs to flip the coordinates
   fragUV = vec2(vertexUV.x, 1.0 - vertexUV.y);
}

我可以看到图像有些“扭曲”，因为它仍将透视图呈现为正交图像。如果删除x轴上的旋转，则不再压缩它，因为它根本没有放下。对我在做什么错有任何想法吗？我可以根据要求提供更多信息，但我想我投入了很多东西。

图片：

Answer 1

您不应该修改gl_Position.w

    gl_Position = M * V * P * vec4(vertexPosition, 1.0); // gl_Position is good

    //indicate that the coordinates are nomalized < not true
    gl_Position.w = 1.0; // Now perspective divisor is lost, projection isn't correct