Camera and Cube Overlapping

OpenGL
1

Hello, I’m trying to create a function that check if my camera is touching one of the cubes ( array ).
I thought about doing distance between MVP / View Matrix and Model and if it’s equal to “0 + scale” / “0 - scale” it’s overlapping.
but somehow it doesn’t work…

Camera Update Source:

void Camera::Update(glm::vec3 const& Cube_scale,
					glm::vec3 const& Cube_position)
{
	Camera::computeMatricesFromInputs();

	glm::mat4 Model = glm::mat4();
	Model = glm::scale(Model, Cube_scale);
	Model = glm::translate(Model, Cube_position);
	glm::mat4 mvp = ProjectionMatrix * ViewMatrix * Model;

	glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &mvp[0][0]);

	// Overlap Detection - will moved to function
	float dist = Distance3D(Model[3][0], mvp[3][0], Model[3][1], mvp[3][1], Model[3][2], mvp[3][2]);
        std::cout << dist << std::endl; 
}

but the values aren’t correct.
by the way, I’ve seen something about “extracting” translation from matrices, so i guess i need to do something with that, but not sure how.

can anyone direct me to the correct path ? or give me an example ? ( it would be great ).

2

The vector from the eye to the centre of the cube is (ViewMatrix * Model)[3], or ViewMatrixModelvec4(0,0,0,1). So you just need the length of that vector. E.g.


float distance = glm::length(glm::vec3((ViewMatrix * Model)[3]));
3

[QUOTE=GClements;1289575]The vector from the eye to the centre of the cube is (ViewMatrix * Model)[3], or ViewMatrixModelvec4(0,0,0,1). So you just need the length of that vector. E.g.


float distance = glm::length(glm::vec3((ViewMatrix * Model)[3]));

[/QUOTE]

i have tested what you said with my project and it FINALLY worked!
i didn’t know about glm::length, i really should spend some time in GLM library xD