Opengl 模型视图投影中的第四行是否为查看位置?
我想从摄影机的方向照亮顶点级别的平面。当我旋转视图时,我希望照明不会改变,但当我稍微看向别处时,它是最亮的。mvp[3]不是我认为的摄像机坐标吗Opengl 模型视图投影中的第四行是否为查看位置?,opengl,glsl,shader,coordinate-transformation,perspectivecamera,Opengl,Glsl,Shader,Coordinate Transformation,Perspectivecamera,我想从摄影机的方向照亮顶点级别的平面。当我旋转视图时,我希望照明不会改变,但当我稍微看向别处时,它是最亮的。mvp[3]不是我认为的摄像机坐标吗 #version 450 in vec3 vertex; uniform mat4 mvp; out vec4 color; void main() { gl_Position = mvp * vec4(vertex,1.); vec3 n = vec3(0.,0.,1.); vec3 v = normalize( vec3
#version 450
in vec3 vertex;
uniform mat4 mvp;
out vec4 color;
void main()
{
gl_Position = mvp * vec4(vertex,1.);
vec3 n = vec3(0.,0.,1.);
vec3 v = normalize( vec3(mvp[3])-vertex );
//I tried the other direction in the mat4
//vec3(mvp[0][3],mvp[1][3],mvp[2][3]);
color = vec4( dot(v,n) );
}
模型视图投影矩阵中的第4列是否为查看位置
不,不是。视图矩阵的第4列将包含摄影机位置,但模型视图投影矩阵是模型矩阵、视图矩阵和投影矩阵的组合
视图矩阵通常如下所示:
mat4 view;
view[0] : ( X-axis.x, X-axis.y, X-axis.z, 0 )
view[1] : ( Y-axis.x, Y-axis.y, Y-axis.z, 0 )
view[2] : ( Z-axis.x, Z-axis.y, Z-axis.z, 0 )
view[3] : ( trans.x, trans.y, trans.z, 1 )
r = right, l = left, b = bottom, t = top, n = near, f = far
mat4 projection;
projection[0] : 2*n/(r-l) 0 0 0
projection[1] : 0 2*n/(t-b) 0 0
projection[2] : (r+l)/(r-l) (t+b)/(t-b) -(f+n)/(f-n) -1
projection[3] : 0 0 -2*f*n/(f-n) 0
mat4 matA;
mat4 matB;{
mat4 matC;
for ( int i0 = 0; i0 < 4; ++ i0 )
for ( int i1 = 0; i1 < 4; ++ i1 )
matC[i0][i1] = matB[i0][0] * matA[0][i1] + matB[i0][1] * matA[1][i1] + matB[i0][2] * matA[2][i1] + matB[i0][3] * matA[3][i1];
透视投影矩阵可能如下所示:
mat4 view;
view[0] : ( X-axis.x, X-axis.y, X-axis.z, 0 )
view[1] : ( Y-axis.x, Y-axis.y, Y-axis.z, 0 )
view[2] : ( Z-axis.x, Z-axis.y, Z-axis.z, 0 )
view[3] : ( trans.x, trans.y, trans.z, 1 )
r = right, l = left, b = bottom, t = top, n = near, f = far
mat4 projection;
projection[0] : 2*n/(r-l) 0 0 0
projection[1] : 0 2*n/(t-b) 0 0
projection[2] : (r+l)/(r-l) (t+b)/(t-b) -(f+n)/(f-n) -1
projection[3] : 0 0 -2*f*n/(f-n) 0
mat4 matA;
mat4 matB;{
mat4 matC;
for ( int i0 = 0; i0 < 4; ++ i0 )
for ( int i1 = 0; i1 < 4; ++ i1 )
matC[i0][i1] = matB[i0][0] * matA[0][i1] + matB[i0][1] * matA[1][i1] + matB[i0][2] * matA[2][i1] + matB[i0][3] * matA[3][i1];
矩阵乘法的工作原理如下:
mat4 view;
view[0] : ( X-axis.x, X-axis.y, X-axis.z, 0 )
view[1] : ( Y-axis.x, Y-axis.y, Y-axis.z, 0 )
view[2] : ( Z-axis.x, Z-axis.y, Z-axis.z, 0 )
view[3] : ( trans.x, trans.y, trans.z, 1 )
r = right, l = left, b = bottom, t = top, n = near, f = far
mat4 projection;
projection[0] : 2*n/(r-l) 0 0 0
projection[1] : 0 2*n/(t-b) 0 0
projection[2] : (r+l)/(r-l) (t+b)/(t-b) -(f+n)/(f-n) -1
projection[3] : 0 0 -2*f*n/(f-n) 0
mat4 matA;
mat4 matB;{
mat4 matC;
for ( int i0 = 0; i0 < 4; ++ i0 )
for ( int i1 = 0; i1 < 4; ++ i1 )
matC[i0][i1] = matB[i0][0] * matA[0][i1] + matB[i0][1] * matA[1][i1] + matB[i0][2] * matA[2][i1] + matB[i0][3] * matA[3][i1];
mvp[3]是第四列,而不是第四行。请参阅