原博客:http://blog.csdn.net/qq_23225317/article/details/65937396
include “glm/glm.hpp”
include “glm/gtc/matrix_transform.hpp”
若未特別說明,以下示例均假設矩陣/向量爲四維
glm::mat4 mat;
glm::vec4 vec;
對於vec來說,第四位爲1代表座標,0代表方向
平移矩陣
| 1 0 0 X |
| 0 1 0 Y |
| 0 0 1 Z |
| 0 0 0 1 |
構造平移矩陣
glm::mat4 mat = glm::translate(X, Y, Z);
拉伸矩陣
| x 0 0 0 |
| 0 y 0 0 |
| 0 0 z 0 |
| 0 0 0 1 |
構造拉伸矩陣
glm:mat4 mat = glm::scale(x, y, z);
旋轉矩陣
若轉軸爲 x, y, z, 角度爲 a
X = x sin(a), Y = y sin(a), Z = z sin(a), W = cos(a)
| 1 - 2(Y*Y+Z*Z) | 2(X*Y+Z*W) | 2(X*Z-Y*W) | 0 |
| 2(X*Y-Z*W) | 1 - 2(X*X+Z*Z) | 2(Y*Z+X*W) | 0 |
| 2(X*Z+Y*W) | 2(Y*Z-X*W) | 1 - 2(X*X+Y*Y) | 0 |
| 0 | 0 | 0 | 1 |
構造旋轉矩陣
glm::vec3 axis(x, y, z);
glm::mat4 transformedMatrix = glm::rotate(mat, a, axis);
初等變換矩陣與座標相乘可得變換後的座標
mat * vec (= vec)
glm::vec4 transformedVector = mat * vec;
構造模型矩陣
glm::mat4 mat = transmat3 * transmat2 * transmat1 * mat;
構造視圖矩陣
glm::mat4 mat = glm::LookAt(CameraPos, CameraTarget, upVector);
若相機正置,則 upVector = glm:vec3(0, 1, 0)
構造投影矩陣
glm::mat4 mat = glm::perspective(FoV, AspectRatio, NearClipPlane, FarClipPlane);
模型矩陣 視圖矩陣 投影矩陣
- 1
- 2
模型座標 ———-> 絕對座標 ———-> 相機座標 ———-> 齊次座標
最後一步是用仿射變換模擬人眼成像的過程
glm:mat3 MVP = projection * view * model;
循環前註冊句柄
GLuint MatrixID = glGetUniformLocation(programID, “MVP”);
循環中傳遞給GLSL
glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);
GLSL vertex shader 末期處理
layout(location = 0) in vec3 vertexPosition_modelspace;
uniform mat4 MVP;
void main()
{
vec4 v = vec4(vertexPosition_modelspace, 1);
gl_Position = MVP * v;
}