Jump to content

Math Challenge Lens Shader


Recommended Posts

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);

 

Edited by Alan Monroig
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...