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About kreaThor

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  1. ok U guys thanks. I will delve some more into the topic, though I understood from haegarr that it can't be done in opengl.
  2. Hello! I saw some very interesting pictures of a cube drawn by projecting it with a perspective projection with more than one vanishing point. Can this be done in OpenGL? If yes, how can the projection matrix be calculated?
  3. kreaThor

    custom projection matrix

    anyone any ideas? to be more specific: I want to use the following matrix as a perspective matrix: GLdouble g_dOblicProj[]={ 1 , 0 , -0.5 , 0 , 0 , 1 , 3.25 , 0 , 0 , 0 , 0 , 0, 0 , 0 , 0 , 1 }; I load this one using glLoadmatrix, but the result looks the same as though I were using glOrtho :( I can do the math in order to compute the matrices of various projection matrices, but I don't understand how can I define the "viewing volume" - the one that is a frustum in perspective projection, and a box in orthographic projection
  4. Hello everyone! I want to create a custom projection matrix, and load it with glLoadMatrix* function. There are two difficulties that I encountered: 1) I have found no guidelines for doing this in the red book, at the viewing chapter. So I started searching the web, but I found nothing that would satisfy me. My problem is that I am really used to OpenGL GlFrustum and glOrtho calls to change the projection matrix, which define a "canonical volume" for viewing,and I don't really understand how I can use glLoadMatrix to load a matrix, and to "bypass" the canonical volume stuff. 2) I read in an article on the net - sorry I don't know how to use VB codes on this forum , are they turned on? - http://sjbaker.org/steve/omniv/projection_abuse.html I read here that "You *could* use glLoadMatrix to set up your own projection matrix (if you understand the restrictions and consequences)" So what are those "restrictions and consequences"? 3) Even though I am interested in the general aspect of the problem, I can be even more specific: I want to use in an opengl app an "oblique projection". Has anyone any idea how this can be done in OpenGL - an axonometric projection with default parameters, let's make it like an orthographic projection, but the angle between the normal and the viewing direction to be say 60 degrees - can anyone tell me how this can be done, eventually with some sample source code?
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