将图像从屏幕坐标转换为世界坐标

Question

我正试图编写一个函数，在给定的屏幕坐标下绘制图像，并将其放置在OpenGL中的世界坐标中。

glm::vec3 CImage::showImage(float x, float y)
{
float screenW = 1920.0f;
float screenH = 1080.0f;
float xPosition = x;
float yPosition = y;
xPosition = xPosition * 2 / screenW - 1;
yPosition = yPosition * (-2 / screenH) + 1;
glm::vec4 viewport = glm::vec4(0.0f, 0.0f, screenW, screenH);
glm::mat4 projectionMatrix = glm::ortho(0.0f, screenW, screenH, 0.0f, -1.0f, 1.0f);
glm::mat4 model = glm::mat4(1.0f);
glm::vec2 pixel_pos = glm::vec2(xPosition, screenH - yPosition);
glm::vec3 world = glm::unProject(glm::vec3(pixel_pos, 0), model, projectionMatrix, viewport);
return world;
}

由调用

glm::mat4 transform = glm::mat4(1.0f);
transform = glm::translate(transform, showImage(100, 150));//screen coordinates
glUseProgram(shaderProgram);
unsigned int transformLoc = glGetUniformLocation(shaderProgram, "transform");
glUniformMatrix4fv(transformLoc, 1, GL_FALSE, glm::value_ptr(transform));
glBindVertexArray(vao);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

这是顶点着色器：

#version 330
layout(location = 0) in vec3 aPos;
layout(location = 1) in vec2 aTexCoord;
out vec2 TexCoord;
uniform mat4 transform;
void main() 
{
gl_Position = transform * vec4(aPos, 1.0);
TexCoord = vec2(aTexCoord.x, aTexCoord.y);
};

这是片段着色器：

#version 330
out vec4 FragColor;
in vec2 TexCoord;
uniform sampler2D texture_sampler;
void main() 
{
FragColor = texture(texture_sampler, TexCoord);
};

根据图像大小的不同，结果从来都不一样，如果我把它放在中间(960540(，它会起作用，但当我试图在左/上角或右/下角显示时，它会一团糟。我知道(glm::unproject(有几个这样的问题，但我已经试了好几天来解决它了

Answer 1

回答我自己的问题：

glm::vec3 CImage::showImage(float x, float y)
{
float screenW = 1920;
float screenH = 1080;
float xPosition = x;
float yPosition = y;
float sxImage = 100; 
float syImage = 100; 
xPosition = xPosition * 2 / screenW - 1;
yPosition = yPosition * (-2 / screenH) + 1;
glm::vec4 viewport = glm::vec4(0.0f, 0.0f, screenW, screenH);
glm::mat4 projectionMatrix = glm::ortho(0.0f, screenW, screenH, 0.0f, -1.0f, 1.0f);
glm::mat4 model = glm::mat4(1.0f);
glm::vec2 pixel_pos = glm::vec2(xPosition, screenH - yPosition);
pixel_pos = pixel_pos + glm::vec2(sxImage / screenW, syImage / screenH);
glm::vec3 world = glm::unProject(glm::vec3(pixel_pos, 0), model, projectionMatrix, viewport);
return world;
}