3D场景转换不太工作 [英] 3D Scene transformations not quite working

问题描述

为了将屏幕空间坐标转换为世界空间坐标，我已经进行了以下计算：

In an attempt to convert screen space coordinates into world space coordinates, I've been doing the following calculation:

WorldSpace Vector = inverse（Projection Matrix）* inverse （View Matrix）* ScreenSpace向量

WorldSpace Vector = inverse(Projection Matrix) * inverse(View Matrix) * ScreenSpace vector

到现在为止，我相信我的大部分计算都是正确的，但是我不知道如何执行最后一步。

Up to this point, I believe I have most of my calculations right, however I'm unsure of how to perform the last step needed in order to have my vector transformed to world coordinates.

问题：

• 我被告知，这个过程的最后一步是将我的结果除以变量w，因为我们使用齐次坐标。但是我不知道w代表什么。

我定义了以下变量（x和y是鼠标坐标的整数）：

I've defined the following variables (x and y are integers of the mouse coordinates):

GLint viewport[4];
GLfloat winX, winY;
glGetIntegerv(GL_VIEWPORT, viewport);

winX = ((float)x/viewport[2]*2)-1;
winY = ((float)(viewport[3]-y)/viewport[3]*2)-1;

glm::mat4x4 mMatrix;
glm::mat4x4 vMatrix;

glm::mat4x4 cameraTransformation;

我进行了以下转换：

cameraTransformation = glm::rotate(cameraTransformation, (float)alpha*(float)M_PI/180, glm::vec3(0, 1, 0));
cameraTransformation = glm::rotate(cameraTransformation, (float)beta*(float)M_PI/180, glm::vec3(1, 0, 0));

glm::vec4 cameraPosition = (cameraTransformation * glm::vec4(camX, camY, distance, 0));
glm::vec4 cameraUpDirection = cameraTransformation * glm::vec4(0, 1, 0, 0);

vMatrix = glm::lookAt(glm::vec3(cameraPosition[0],cameraPosition[1],cameraPosition[2]), glm::vec3((float)camX, (float)camY, 0.0), glm::vec3(cameraUpDirection[0],cameraUpDirection[1],cameraUpDirection[2]));

glm::mat4x4 mat =  glm::inverse(vMatrix) * glm::inverse(mMatrix) * glm::inverse(pMatrix);
glm::vec4 wSC = (mat) * glm::vec4(winX,winY,0,0);

在我的resize事件中，我的pMatrix预计为：

In my resize event, my pMatrix is projected as such:

pMatrix = glm::mat4x4(1.0);//sets identity
pMatrix = glm::perspective( (float)fov*(float)M_PI/180, (float) width / (float) height, (float)0.001, (float)10000 );

注意：我过去使用GLU库有问题，显然使用unProject功能，所以我选择自己执行计算。

Note: I've had issues in the past with using the GLU library, and apparently with using unProject functions overall, so I've elected to perform the calculations myself. At this point its almost a justification of effort, but I'm not going to use preexisting unprojection functions period.

推荐答案

在这个例子中，我的光线选择问题的最后阶段，我被告知我做错了几个事情：

In this last stage of my ray picking problem, I was informed that I was doing several things wrong:

1. 我的z坐标应该是-1，而不是0


2. 提醒我需要在相对平面上有2个独立的向量，不要只使用1来进行测试，而是通过实际的光线选择器来运行它工作原理。


3. 使用w值为1，而不是0.这是 glm :: vec4 wSC =（mat）* glm的最后一个位置： ：vec4（winX，winY，0,0）; 行。


4. 我需要在执行任何计算之前将鼠标坐标转换为NDC坐标， is：
   
   
   
   • 将鼠标x除以屏幕宽度，乘以2，减1。
   
   
   • 从 >屏幕高度，除以屏幕高度，乘以2，减去1： winX =（（float）x / viewport [2] * 2）-1;
winY =（（float）（viewport [3] -y）/ viewport [3] * 2）-1;
   
   

1. My z coordinate for a window space near plane should be -1, not 0
2. Reminder that I need 2 separate vectors at the opposing planes, don't just use 1 for testing, run it through the actual ray picker to see if it works.
3. Use a "w" value of 1, not 0. This is the last spot of the glm::vec4 wSC = (mat) * glm::vec4(winX,winY,0,0); line.
4. That I need to convert my mouse coordinates into NDC coordinates before performing any calculations, so this is:
   • divide mouse x by screen width, times 2, minus 1.
   • subtract mouse y from screen height, divide by screen height, times 2, minus 1: winX = ((float)x/viewport[2]*2)-1; winY = ((float)(viewport[3]-y)/viewport[3]*2)-1;

由于我的问题延续了相当长的时间，并且遇到了几个问题，我欠几个帮助我的人方式：

Since my problem extended over quite a great length of time, and took up several questions, I owe credit to a few individuals who helped me along the way:

• sapsins of facepunch ，in this thread


• 从这里解开，在此问题和此讨论

• srobins of facepunch, in this thread
• derhass from here, in this question, and this discussion

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