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#ActualNaked Shooter

Posted 21 October 2012 - 04:16 PM

Hi. I'm trying to get the frustum vertices by using the perspective projection matrix's inverse. I'm trying to take a cube with the vertices { (-1,-1,-1), (1,-1,-1) ... } and multiply each vertex by the inverse of the perspective matrix, hoping to get the frustum. This isn't working, however. I am aware that there's a lighthouse3d tutorial, and I just might bite the bullet and go through it, but I'm just curious why this isn't working.

glm::mat4 projection(0);
glm::mat4 projectionInv(0);
//the frustum in normalized coordinates
vector<glm::vec4> NDCCube;
NDCCube.push_back(glm::vec4(-1.0f, -1.0f, -1.0f, 1.0f));
NDCCube.push_back(glm::vec4(1.0f, -1.0f, -1.0f, 1.0f));
NDCCube.push_back(glm::vec4(1.0f, -1.0f, 1.0f, -0.0f));
NDCCube.push_back(glm::vec4(-1.0f, -1.0f, 1.0f, -0.0f));
NDCCube.push_back(glm::vec4(-1.0f, 1.0f, -1.0f, 1.0f));
NDCCube.push_back(glm::vec4(1.0f, 1.0f, -1.0f, 1.0f));
NDCCube.push_back(glm::vec4(1.0f, 1.0f, 1.0f, -0.0f));
NDCCube.push_back(glm::vec4(-1.0f, 1.0f, 1.0f, -0.0f));
/* Get the current PROJECTION from OpenGL */
glGetFloatv(GL_PROJECTION_MATRIX, (GLfloat*)(glm::value_ptr(projection)));
//calculate the inverse of projection matrix. Hopefully, this'll get us the frustum when multiplied
//by coords of a cube.
projectionInv = glm::inverse(projection);

//push back vertices
for(int i = 0; i < 8; i++)
{
  glm::vec4 tempvec;
  tempvec = projectionInv * NDCCube.at(i); //multiply by projection matrix inverse to obtain frustum vertex
  frustumVertices.push_back(Vector3(tempvec.x, tempvec.y, tempvec.z));
}

#2Naked Shooter

Posted 21 October 2012 - 03:40 PM

Hi. I'm trying to get the frustum vertices by using the perspective projection matrix's inverse. I'm trying to take a cube with the vertices { (-1,-1,-1), (1,-1,-1) ... } and multiply each vertex by the inverse of the perspective matrix, hoping to get the frustum. This isn't working, however. Am I missing something?

glm::mat4 projection(0);
glm::mat4 projectionInv(0);
//the frustum in normalized coordinates
vector<glm::vec4> NDCCube;
NDCCube.push_back(glm::vec4(-1.0f, -1.0f, -1.0f, 1.0f));
NDCCube.push_back(glm::vec4(1.0f, -1.0f, -1.0f, 1.0f));
NDCCube.push_back(glm::vec4(1.0f, -1.0f, 1.0f, -0.0f));
NDCCube.push_back(glm::vec4(-1.0f, -1.0f, 1.0f, -0.0f));
NDCCube.push_back(glm::vec4(-1.0f, 1.0f, -1.0f, 1.0f));
NDCCube.push_back(glm::vec4(1.0f, 1.0f, -1.0f, 1.0f));
NDCCube.push_back(glm::vec4(1.0f, 1.0f, 1.0f, -0.0f));
NDCCube.push_back(glm::vec4(-1.0f, 1.0f, 1.0f, -0.0f));
/* Get the current PROJECTION from OpenGL */
glGetFloatv(GL_PROJECTION_MATRIX, (GLfloat*)(glm::value_ptr(projection)));
//calculate the inverse of projection matrix. Hopefully, this'll get us the frustum when multiplied
//by coords of a cube.
projectionInv = glm::inverse(projection);

//push back vertices
for(int i = 0; i < 8; i++)
{
  glm::vec4 tempvec;
  tempvec = projectionInv * NDCCube.at(i); //multiply by projection matrix inverse to obtain frustum vertex
  frustumVertices.push_back(Vector3(tempvec.x, tempvec.y, tempvec.z));
}

#1Naked Shooter

Posted 21 October 2012 - 03:39 PM

Hi. I'm trying to get the frustum vertices by using the perspective projection matrix's inverse. I'm trying to take a cube with the vertices { (-1,-1,-1), (1,-1,-1) ... } and multiply each vertex by the inverse of the perspective matrix, hoping to get the frustum. This isn't working, however. Am I missing something?

glm::mat4 projection(0);
glm::mat4 projectionInv(0);
//the frustum in normalized coordinates
vector<glm::vec4> NDCCube;
NDCCube.push_back(glm::vec4(-1.0f, -1.0f, -1.0f, 1.0f));
NDCCube.push_back(glm::vec4(1.0f, -1.0f, -1.0f, 1.0f));
NDCCube.push_back(glm::vec4(1.0f, -1.0f, 1.0f, -0.0f));
NDCCube.push_back(glm::vec4(-1.0f, -1.0f, 1.0f, -0.0f));
NDCCube.push_back(glm::vec4(-1.0f, 1.0f, -1.0f, 1.0f));
NDCCube.push_back(glm::vec4(1.0f, 1.0f, -1.0f, 1.0f));
NDCCube.push_back(glm::vec4(1.0f, 1.0f, 1.0f, -0.0f));
NDCCube.push_back(glm::vec4(-1.0f, 1.0f, 1.0f, -0.0f));
/* Get the current PROJECTION and MODELVIEW matrices from OpenGL */
glGetFloatv(GL_PROJECTION_MATRIX, (GLfloat*)(glm::value_ptr(projection)));
//calculate the inverse of projection matrix. Hopefully, this'll get us the frustum when multiplied
//by coords of a cube.
projectionInv = glm::inverse(projection);

//push back vertices
for(int i = 0; i < 8; i++)
{
  glm::vec4 tempvec;
  tempvec = projectionInv * NDCCube.at(i); //multiply by projection matrix inverse to obtain frustum vertex
  frustumVertices.push_back(Vector3(tempvec.x, tempvec.y, tempvec.z));
}

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