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Found 5 results

  1. Math Challenge Lens Shader

    Hello! I am struggling to get what I want from a lens shader. It is somehow a math challenge. Let's see if there is someone who can figure it out... Simple scenario: - Perspective camera looking towards a grid made of 4 points (corners). - I want the camera to render the grid taking each corner as a reference to fill the frame completely with the grid (not more or less). Details: - The grid should be able to rotate on 3 axes and the camera should keep framing it. (So aspect ratio won't do it, since it has some perspective). - I have managed to do it in one axis, but additional axes seem to start acting weird, the results are close but not enough. Since it is math it should be perfect! (I does not have to be foolproof, looking towards the Z direction always and not handling more than 180-degree rotations is ok). Code of my lens shader #include "math.h" #pragma opname lens_shader #pragma oplabel "Lens_shader" #pragma hint x hidden #pragma hint y hidden #pragma hint Time hidden #pragma hint dofx hidden #pragma hint dofy hidden #pragma hint aspect hidden #pragma hint P hidden #pragma hint I hidden cvex anamorphic_lens( //Inputs float x = 0; // X screen coordinate in the range -1 to 1 float y = 0; // Y screen coordinate in the range -1 to 1 float Time = 0; // Sample time float dofx = 0; // X depth of field sample value float dofy = 0; // Y depth of field sample value float aspect = 1; // Image aspect ratio (x/y) //Outputs export vector P = 0; // Ray origin in camera space export vector I = 0; // Ray direction in camera space export int valid = 1; // Whether the sample is valid for measuring //Grid corners converted to camera space vector corner0 = 0; vector corner3 = 0; ) { float xmin_bounds = corner0[0]; float xmax_bounds = corner3[0]; float ymin_bounds = corner0[1]; float ymax_bounds = corner3[1]; float zmin_bounds = corner0[2]; float zmax_bounds = corner3[2]; float new_x = fit(x, -1, 1, min(xmin_bounds, xmax_bounds), max(xmin_bounds, xmax_bounds)); float new_y = fit(y, -1, 1, min(ymin_bounds, ymax_bounds), max(ymin_bounds, ymax_bounds)); // Calculations Z axis in relation to X float offset = min(zmin_bounds, zmax_bounds); float relation_x = (max(zmin_bounds, zmax_bounds)-offset)/min(xmin_bounds, xmax_bounds); if(xmin_bounds > xmax_bounds){ relation_x *= -1; } float relation_y = (max(zmin_bounds, zmax_bounds)-offset)/min(ymin_bounds, ymax_bounds); if(ymin_bounds > ymax_bounds){ relation_y *= -1; } float z = (-relation_x * new_x) + (-relation_y * new_y) + offset; P = set(0, 0, 0); I = set(new_x, new_y, z);
  2. Anamorphic Lens Squeeze

    I know this is a bit of a bizarre request but I'm trying to simulate rendering in anamorphic squeezed, to later be unsqueezed in comp. I've set up my resolutions and pixel aspect ratio but as expected it just reframes the image and doesn't provide that squeezing effect you might get from something similar to Maya's lens squeeze parameter? Any advice on how to achieve this? Thanks!
  3. 2 point perspective correction Hello everyone, Is there a 3ds Max 2 point perspective correction feature in houdini? I did not find it in the houdini camera parameters. Or can you do something like 2 point perspective correction with houdini? I do not have much knowledge and I would be happy if someone could solve this problem and help. Thank you.
  4. is it possible to tilt-shift the lens somehow in houdini to force this effect ? kind regards Jon
  5. Hello, I am not sure in which category this question is supposed to go. I have an explosion with a very low angle (a lot of sky) and can't decide whether to use a small or big focal length to communicate a nice, massive blow! Is there a rule of thumb for this? Thanks