Inverse Scissoring

[memononen]

Inverse Scissoring

[memononen]

There's currently no way of doing it, but it should be possible to add. For reverse scissor, this line:
" sc = vec2(0.5,0.5) - sc * scissorScale;\n"
probably should become:
" sc = sc * scissorScale + vec2(0.5,0.5);\n"
I have to double check that. Making stuff properly AA is sometimes a bit tricky.

Out of curiosity how do you plan to use it?

[devnought]

Instead of calculating where two lines intersect (line into the box in this example) and only drawing to the edge of the box, was thinking of cheaping out just drawing how it's being drawn here, except the interior of the box would be the scissored out area :)

[memononen]

Maybe you can use raycasting instead of clipping? You'll get 2 intersection points and probably want to draw the line from lerp(sp, sq, tmax) to sq. Could this work? :)

int isectSegRect(const float* sp, const float* sq,
         const float* amin, const float* amax,
         float* tmin, float* tmax)
{
    static const float EPS = 1e-6f;
    float d[2];
    d[0] = sq[0] - sp[0];
    d[1] = sq[1] - sp[1];
    *tmin = -FLT_MAX;
    *tmax = FLT_MAX;

    // For all three slabs
    for (int i = 0; i < 2; i++)
    {
        if (fabsf(d[i]) < EPS)
        {
            // Ray is parallel to slab. No hit if origin not within slab
            if (sp[i] < amin[i] || sp[i] > amax[i])
                return 0;
        }
        else
        {
            // Compute intersection t value of ray with near and far plane of slab
            const float ood = 1.0f / d[i];
            float t1 = (amin[i] - sp[i]) * ood;
            float t2 = (amax[i] - sp[i]) * ood;
            // Make t1 be intersection with near plane, t2 with far plane
            if (t1 > t2) swap(t1, t2);
            // Compute the intersection of slab intersections intervals
            if (t1 > *tmin) *tmin = t1;
            if (t2 < *tmax) *tmax = t2;
            // Exit with no collision as soon as slab intersection becomes empty
            if (*tmin > *tmax) return 0;
        }
    }
    return 0;
}

[devnought]

That does work! Thanks! :)