我正在尝试使用 OpenGL 和 C++ 制作一个简单的体素引擎。我的第一步是从相机发出光线并检测光线是否与某物相交(出于测试目的,它只有两个平面)。我通过创建一个全屏四边形并编程片段着色器为每个片段(现在我只是假设一个片段是一个像素)发送一个在 texCoord 方向上的射线,让它在没有相机旋转的情况下工作。 x,texCoord.y,-1。现在我正在尝试实现相机旋转。
我试图在 cpu 中生成一个旋转矩阵并将其发送到着色器,它将与每条光线相乘。然而,当我旋转相机时,平面开始以一种我只能用这个视频来描述的方式拉伸(stretch)。
https://www.youtube.com/watch?v=6NScMwnPe8c
这是创建矩阵并在每一帧运行的代码:
float pi = 3.141592;
// camRotX and Y are defined elsewhere and can be controlled from the keyboard during runtime.
glm::vec3 camEulerAngles = glm::vec3(camRotX, camRotY, 0);
std::cout << "X: " << camEulerAngles.x << " Y: " << camEulerAngles.y << "\n";
// Convert to radians
camEulerAngles.x = camEulerAngles.x * pi / 180;
camEulerAngles.y = camEulerAngles.y * pi / 180;
camEulerAngles.z = camEulerAngles.z * pi / 180;
// Generate Quaternian
glm::quat camRotation;
camRotation = glm::quat(camEulerAngles);
// Generate rotation matrix from quaternian
glm::mat4 camToWorldMatrix = glm::toMat4(camRotation);
// No transformation matrix is created because the rays should be relative to 0,0,0
// Send the rotation matrix to the shader
int camTransformMatrixID = glGetUniformLocation(shader, "cameraTransformationMatrix");
glUniformMatrix4fv(camTransformMatrixID, 1, GL_FALSE, glm::value_ptr(camToWorldMatrix));
和片段着色器:
#version 330 core
in vec4 texCoord;
layout(location = 0) out vec4 color;
uniform vec3 cameraPosition;
uniform vec3 cameraTR;
uniform vec3 cameraTL;
uniform vec3 cameraBR;
uniform vec3 cameraBL;
uniform mat4 cameraTransformationMatrix;
uniform float fov;
uniform float aspectRatio;
float pi = 3.141592;
int RayHitCell(vec3 origin, vec3 direction, vec3 cellPosition, float cellSize)
{
if(direction.z != 0)
{
float multiplicationFactorFront = cellPosition.z - origin.z;
if(multiplicationFactorFront > 0){
vec2 interceptFront = vec2(direction.x * multiplicationFactorFront + origin.x,
direction.y * multiplicationFactorFront + origin.y);
if(interceptFront.x > cellPosition.x && interceptFront.x < cellPosition.x + cellSize &&
interceptFront.y > cellPosition.y && interceptFront.y < cellPosition.y + cellSize)
{
return 1;
}
}
float multiplicationFactorBack = cellPosition.z + cellSize - origin.z;
if(multiplicationFactorBack > 0){
vec2 interceptBack = vec2(direction.x * multiplicationFactorBack + origin.x,
direction.y * multiplicationFactorBack + origin.y);
if(interceptBack.x > cellPosition.x && interceptBack.x < cellPosition.x + cellSize &&
interceptBack.y > cellPosition.y && interceptBack.y < cellPosition.y + cellSize)
{
return 2;
}
}
}
return 0;
}
void main()
{
// For now I'm not accounting for FOV and aspect ratio because I want to get the rotation working first
vec4 beforeRotateRayDirection = vec4(texCoord.x,texCoord.y,-1,0);
// Apply the rotation matrix that was generated on the cpu
vec3 rayDirection = vec3(cameraTransformationMatrix * beforeRotateRayDirection);
int t = RayHitCell(cameraPosition, rayDirection, vec3(0,0,5), 1);
if(t == 1)
{
// Hit front plane
color = vec4(0, 0, 1, 0);
}else if(t == 2)
{
// Hit back plane
color = vec4(0, 0, 0.5, 0);
}else{
// background color
color = vec4(0, 1, 0, 0);
}
}
最佳答案
好的。真的很难知道什么是错的,但我会尝试。
以下是一些提示和注意事项:
1) 您可以通过将方向映射到 RGB 颜色来调试方向。请记住,您应该标准化 (-1,1)
中的 vector 和映射。至(0,1)
.只需执行 dir*0.5+1.0
类型的东西。例子:
color = vec4(normalize(rayDirection) * 0.5, 0) + vec4(1);
2)您可以以更直接的方式获得旋转矩阵。四元数从正向初始化,它首先会绕 Y 轴旋转(水平方向)然后,只有这样 ,围绕 X 轴(垂直外观)。请记住,如果您从欧拉角初始化,则旋转顺序取决于实现。尽可能使用 mat4_cast 避免实验性 glm 扩展 (gtx)。例子:
// Define rotation quaternion starting from look rotation
glm::quat camRotation = glm::vec3(0, 0, 0);
camRotation = glm::rotate(camRotation, glm::radians(camRotY), glm::vec3(0, 1, 0));
camRotation = glm::rotate(camRotation, glm::radians(camRotX), glm::vec3(1, 0, 0));
glm::mat4 camToWorldMatrix = glm::mat4_cast(camRotation);
3) 您的
beforeRotateRayDirection
是(可能)从 (-1,-1,-1) 一直指向 (1,1,-1) 的 vector 。这是未标准化 , (1,1,1) 的长度为 √3 ≈ 1.7320508075688772...确保您已将其考虑到您的碰撞数学中,或者只是对 vector 进行归一化。到目前为止我的部分答案......
您的碰撞测试有点奇怪......您似乎想将光线转换到给定单元位置的 Z 平面(但两次,一个用于前面,一个用于后面)。我已经查看了您的代码逻辑,它有些道理,但没有顶点程序,因此不知道
texCoord
是什么范围值是,无法确定。您可能想重新考虑您的逻辑,如下所示:int RayHitCell(vec3 origin, vec3 direction, vec3 cellPosition, float cellSize)
{
//Get triangle side vectors
vec3 tu = vec3(cellSize,0,0); //Triangle U component
vec3 tv = vec3(0,cellSize,0); //Triangle V component
//Determinant for inverse matrix
vec3 q = cross(direction, tv);
float det = dot(tu, q);
//if(abs(det) < 0.0000001) //If too close to zero
// return;
float invdet = 1.0/det;
//Solve component parameters
vec3 s = origin - cellPosition;
float u = dot(s, q) * invdet;
if(u < 0.0 || u > 1.0)
return 0;
vec3 r = cross(s, tu);
float v = dot(direction, r) * invdet;
if(v < 0.0 || v > 1.0)
return 0;
float t = dot(tv, r) * invdet;
if(t <= 0.0)
return 0;
return 1;
}
void main()
{
// For now I'm not accounting for FOV and aspect ratio because I want to get the
// rotation working first
vec4 beforeRotateRayDirection = vec4(texCoord.x, texCoord.y, -1, 0);
// Apply the rotation matrix that was generated on the cpu
vec3 rayDirection = vec3(cameraTransformationMatrix * beforeRotateRayDirection);
int t = RayHitCell(cameraPosition, normalize(rayDirection), vec3(0,0,5), 1);
if (t == 1)
{
// Hit front plane
color = vec4(0, 0, 1, 0);
}
else
{
// background color
color = vec4(0, 1, 0, 0);
}
}
这应该给你一架飞机,让我知道它是否有效。立方体将很容易做到。
PS:
u
和 v
可用于纹理映射。
关于c++ - 如何为光线转换生成相机光线,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/61253365/