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Realtime raytracing test

Flash  Flash 10  Pixel Bender  3D 
16 December 2008

Having done a couple of experiments with Pixel Benders (#1, #2), I wanted to throw something more demanding at it.

The problem of doing raytracing in Pixel Benders is the lack of looping, so basically the whole scene would have to be hard-coded. It would be possible to make a generic renderer with some fancy pre-processing of the source code, but it's a big project and the whole effort would be in vain if/when loops are supported in a future version.

Raytracing involves some quite advanced mathematics, so I had to think twice for some of this stuff. A good summary is this document. Initially I wanted to raytrace the torus, but quicky gave up this as I would need to solve this equation, which can only be solved numerically - it's defintely not something I want to do per-pixel. 

I discovered another limitation of Pixel Benders by doing this test: No support for boolean datatype when exporting for Flash (if exporting for After Effects both loops and booleans can be used). It can be a drag when creating optimized SIMD based code, which Pixel Benders supports through the float4 and similar datatypes.

<languageVersion : 1.0;>

 

kernel Crossfade

<   namespace : "SpinningRT";

    vendor : "Spinning Owl";

    version : 1;

    description : "Raytracing for Flash Player 10+. Optimized with faked distance calcs"; >

{   

    parameter float3 sphere1    // (x,y,z) .. radius always = 1

    <

        defaultValue : float3(-.5, 0., 5.);

        minValue : float3(-10., -10., -10.);

        maxValue : float3(10., 10., 10.);

    >;

 

    parameter float3 sphere2    // (x,y,z) .. radius always = 1

    <

        defaultValue : float3(.5, 0., 5.);

        minValue : float3(-10., -10., -10.);

        maxValue : float3(10., 10., 10.);

    >;

 

 

    parameter float2 screensize    // (x,y)

    <

        defaultValue : float2(512., 512.);

        minValue : float2(0., 0.);

        maxValue : float2(2048., 2048.);

    >;

 

    parameter float tweak

    <

        defaultValue : float(1.);

        minValue : float(.2);

        maxValue : float(2.);

    >;

 

 

    output pixel4 dst;

 

    void evaluatePixel()

    {

        // ray of current pixel

        float3 ray_dir = -.5 + float3(outCoord().x / screensize.y, outCoord().y / screensize.y, 2.5);

 

        // Code independent of render path

        float2 aa;

        aa.x = aa.y = dot(ray_dir, ray_dir);

        float2 bb = -2. * float2(dot(ray_dir, sphere1), dot(ray_dir, sphere2));

        float2 root = bb * bb - 4. * aa * (float2(dot(sphere1, sphere1), dot(sphere2, sphere2)) - 1.);

 

 

        // Render paths:

        if(root[0] < 0. && root[1] < 0.)

 

            // No intersections

            dst = pixel4(0., 0., 0., 1.);

 

        else if(root[0] > 0. && root[1] < 0.) {

 

            // Intersecting only 1st sphere

            root[0] = sqrt(root[0]); 

            aa[0] = -.5 / aa[0];

            float2 t = float2((-bb[0] + root[0])*aa[0], (-bb[0] - root[0])*aa[0]);

            dst = pixel4(0., 0., t[1]-t[0], 1.);           

        }

        else if(root[0] < 0. && root[1] > 0.) {

 

            // Intersecting only 2nd sphere

            root[1] = sqrt(root[1]); 

            aa[1] = -.5 / aa[1];

            float2 t = float2((-bb[1] + root[1])*aa[1], (-bb[1] - root[1])*aa[1]);

            dst = pixel4(t[1]-t[0], 0., 0., 1.);

        }           

        else if(root[0] > 0. && root[1] > 0.) {

 

            // Intersecting both spheres

            float2 dist = float2(0., 0.);      // distance travelled inside spheres

            root = sqrt(root);

            aa = -.5 / aa;                 // coefs combined

 

            float2 t1 = (-bb + root)*aa;    // coef of 1st root both spheres

            float2 t2 = (-bb - root)*aa;    // coef of 2nd root both spheres

 

            dist[0] = (t2[0] - t1[0]);      // dist[0] = distance(ray_dir * t1[0], ray_dir * t2[0]);

            dist[1] = (t2[1] - t1[1]);      // dist[1] = distance(ray_dir * t1[1], ray_dir * t2[1]);

 

            if(t2[1] > t2[0])       // apply material properties

                dst = pixel4(dist[1], 0., dist[0]-dist[1]*tweak, 1.);

            else

                dst = pixel4(dist[1]-dist[0]*tweak, 0., dist[0], 1.);

        }

    }   

}

<languageVersion : 1.0;>

 

kernel Crossfade

<   namespace : "SpinningRT";

    vendor : "Spinning Owl";

    version : 1;

    description : "Raytracing for Flash Player 10+. Test #2"; >

{   

    parameter float3 sphere1    // (x,y,z) .. radius always = 1

    <

        defaultValue : float3(-.5, 0., 5.);

        minValue : float3(-10., -10., -10.);

        maxValue : float3(10., 10., 10.);

    >;

 

    parameter float3 sphere2    // (x,y,z) .. radius always = 1

    <

        defaultValue : float3(.5, 0., 5.);

        minValue : float3(-10., -10., -10.);

        maxValue : float3(10., 10., 10.);

    >;

 

 

    parameter float2 screensize    // (x,y)

    <

        defaultValue : float2(512., 512.);

        minValue : float2(0., 0.);

        maxValue : float2(2048., 2048.);

    >;

 

    parameter float2 tweak

    <

        defaultValue : float2(1., .5);

        minValue : float2(.2, 0.);

        maxValue : float2(2., 1.);

    >;

 

 

    output pixel4 dst;

 

    void evaluatePixel()

    {

        // ray of current pixel

        float3 ray_dir = float3(-.5*screensize.x/screensize.y, -.5, 0) + float3(outCoord().x / screensize.y, outCoord().y / screensize.y, 2.);

 

        // Code independent of render path

        float2 aa;

        aa.x = aa.y = dot(ray_dir, ray_dir);

        float2 bb = -2. * float2(dot(ray_dir, sphere1), dot(ray_dir, sphere2));

        float2 root = bb * bb - 4. * aa * (float2(dot(sphere1, sphere1), dot(sphere2, sphere2)) - 1.);

 

 

        // Render paths:

        if(root[0] < 0. && root[1] < 0.)

 

            // No intersections

            dst = pixel4(0., 0., 0., 1.);

 

        else if(root[0] > 0. && root[1] < 0.) {

 

            // Intersecting only 1st sphere

            root[0] = sqrt(root[0]); 

            aa[0] = -.5 / aa[0];

            float2 t = float2((-bb[0] + root[0])*aa[0], (-bb[0] - root[0])*aa[0]);

            dst = pixel4(0., 0., t[1]-t[0], 1.);           

        }

        else if(root[0] < 0. && root[1] > 0.) {

 

            // Intersecting only 2nd sphere

            root[1] = sqrt(root[1]); 

            aa[1] = -.5 / aa[1];

            float2 t = float2((-bb[1] + root[1])*aa[1], (-bb[1] - root[1])*aa[1]);

            dst = pixel4(t[1]-t[0], 0., 0., 1.);

        }           

        else if(root[0] > 0. && root[1] > 0.) {

 

            // Intersecting both spheres

            float2 dist;

            root = sqrt(root);

            aa = -.5 / aa;                 // coefs combined

 

            float2 t1 = (-bb + root)*aa;    // coef of 1st root both spheres.

            float2 t2 = (-bb - root)*aa;    // coef of 2nd root both spheres

 

            dist[0] = (t2[0] - t1[0]);      // dist[0] = distance(ray_dir * t1[0], ray_dir * t2[0]);

            dist[1] = (t2[1] - t1[1]);      // dist[1] = distance(ray_dir * t1[1], ray_dir * t2[1]);

 

 

            float dist12;

            float dist_overlap = 0.;

            float dist34;

 

            if(t2[0] > t2[1]) {       // 1st intersection sphere 1 ?

                if(t1[0] < t2[1]) {  

                    // order t2[0], t2[1], t1[0], t1[1]

                    dist12 = t2[0] - t2[1];

                    dist_overlap = t2[1] - t1[0];

                    dist34 = t1[0] - t1[1];

                }

                else {

                    // order t2[0], t1[0], t2[1], t1[1]

                    dist12 = t2[0] - t1[0];

                    dist34 = t2[1] - t1[1];

                }

                dst = pixel4(dist34 + dist_overlap - dist12, 0., dist12+dist_overlap, 1.);

            }

            else { 

                if(t2[0] > t1[1]) {

                    // order t2[1], t2[0], t1[1], t1[0]

                    dist12 = t2[1] - t2[0];

                    dist_overlap = t2[0] - t1[1];

                    dist34 = t1[1] - t1[0];

                }

                else {

                    // order t2[1], t1[1], t2[0], t1[0]

                    dist12 = t2[1] - t1[1];

                    dist34 = t2[0] - t1[0];

                }

                dst = pixel4(dist12+dist_overlap, 0., dist34 + dist_overlap - dist12, 1.);

           }

        }

    }   

 

}

 

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