31

我正在尝试在网上阅读一些 OpenGL 教程。问题是我发现了一些旧的使用gluPerspective(). gluPerspective 在 OpenGL 3.0 中被弃用并在 3.1 中被移除。

我可以改用什么功能？

我正在使用安装了最新 FreeGlut 的 C++。

4

5 回答 5

29

您必须手动计算矩阵，然后将其传递给 OpenGL。

计算矩阵

此代码片段基于gluPerspective 文档。

 void BuildPerspProjMat(float *m, float fov, float aspect,
 float znear, float zfar)
 {
  float f = 1/tan(fov * PI_OVER_360);

  m[0]  = f/aspect;
  m[1]  = 0;
  m[2]  = 0;
  m[3]  = 0;

  m[4]  = 0;
  m[5]  = f;
  m[6]  = 0;
  m[7]  = 0;

  m[8]  = 0;
  m[9]  = 0;
  m[10] = (zfar + znear) / (znear - zfar);
  m[11] = -1;

  m[12] = 0;
  m[13] = 0;
  m[14] = 2*zfar*znear / (znear - zfar);
  m[15] = 0;
 }

有一个名为OpenGL 数学的 C++ 库可能很有用。

在 OpenGL 3.1 中加载矩阵

我还是 OpenGL 3.1 API 的新手，但是您需要更新 GPU 上的矩阵，然后在顶点着色器中使用它来获得正确的视角。以下代码只是使用glUniformMatrix4fv将矩阵加载到视频卡上。

{
  glUseProgram(shaderId);
  glUniformMatrix4fv(glGetUniformLocation(shaderId, "u_proj_matrix"),
                     1, GL_FALSE, theProjectionMatrix);
  RenderObject();
  glUseProgram(0);
}

来自随机博客的简单顶点着色器（通过堆栈溢出找到）。

attribute vec4      a_position;
attribute vec4      a_color;

varying vec4        v_color;

uniform mat4 u_proj_matrix;
uniform mat4 u_model_matrix;

void main() {
  mat4 mvp_matrix = u_proj_matrix * u_model_matrix;
  v_color = a_color;
  gl_Position = mvp_matrix * a_position;
}
于 2010-03-10T17:50:52.943 回答
11

Use GLM. 

glm::mat4 projection = glm::perspective(
  // FOV & aspect
  60.0f, 16.0f / 10.0f, 
  // Near and far planes
  0.001f, 1000f);

// If you're using the now deprecated matrix stacks
glMatrixMode(GL_PROJECTION);
glLoadMatrixf(glm::value_ptr(projection));

// if you're using the new shader based pipelines
GLint projectionUniformLocation = ...;
glUniformMatrix4fv(projectionUniformLocation, 1, GL_FALSE, 
  glm::value_ptr(projection));

Note, if you have GLM_FORCE_RADIANS defined then you should use radians in the perspective function, not degrees...

glm::mat4 projection = glm::perspective(
  // FOV & aspect
  PI / 3.0f, 16.0f / 10.0f, 
  // Near and far planes
  0.001f, 1000f);
于 2013-10-28T23:46:11.920 回答
9

从我的一个旧项目中复制：

// The following code is a fancy bit of math that is eqivilant to calling:
// gluPerspective( fieldOfView/2.0f, width/height , 0.1f, 255.0f )
// We do it this way simply to avoid requiring glu.h
GLfloat zNear = 0.1f;
GLfloat zFar = 255.0f;
GLfloat aspect = float(width)/float(height);
GLfloat fH = tan( float(fieldOfView / 360.0f * 3.14159f) ) * zNear;
GLfloat fW = fH * aspect;
glFrustum( -fW, fW, -fH, fH, zNear, zFar );
于 2010-03-10T14:46:22.713 回答
0

这是 Dan 函数的修改版本，简化了Unspecified Behavior的计算。

void buildPerspProjMat(GLfloat *m, GLfloat fov, GLfloat aspect,
GLfloat znear, GLfloat zfar){

  GLfloat h = tan(fov);
  GLfloat w = h / aspect;
  GLfloat depth = znear - zfar;
  GLfloat q = (zfar + znear) / depth;
  GLfloat qn = 2 * zfar * znear / depth;

  m[0]  = w;  m[1]  = 0;  m[2]  = 0;  m[3]  = 0;

  m[4]  = 0;  m[5]  = h;  m[6]  = 0;  m[7]  = 0;

  m[8]  = 0;  m[9]  = 0;  m[10] = q;  m[11] = -1;

  m[12] = 0;  m[13] = 0;  m[14] = qn;  m[15] = 0;
}
于 2013-10-27T00:22:15.610 回答
-1

Direct3D 文档中记录了各种透视矩阵的公式。

这是D3DXMatrixPerspectiveFovRH右手透视投影矩阵 的公式：

yScale = cot(fovY/2)
xScale = yScale / aspect ratio

xScale     0          0              0
0        yScale       0              0
0        0        zf/(zn-zf)        -1
0        0        zn*zf/(zn-zf)      0
于 2012-12-01T17:45:57.733 回答