path: root/thirdparty/thekla_atlas/nvmesh/raster/Raster.cpp

// This code is in the public domain -- castanyo@yahoo.es

/** @file Raster.cpp
 * @brief Triangle rasterization library using affine interpolation. Not
 * specially optimized, but enough for my purposes.
**/

#include "nvmesh.h" // pch

#include "Raster.h"
#include "ClippedTriangle.h"

#include "nvcore/Utils.h" // min, max

#include "nvmath/Vector.inl"
#include "nvmath/ftoi.h"


#define RA_EPSILON		0.00001f

using namespace nv;
using namespace nv::Raster;

namespace
{
    static inline float delta(float bot, float top, float ih)
    {
        return (bot - top) * ih;
    }

    static inline Vector2 delta(Vector2::Arg bot, Vector2::Arg top, float ih)
    {
        return (bot - top) * ih;
    }

    static inline Vector3 delta(Vector3::Arg bot, Vector3::Arg top, float ih)
    {
        return (bot - top) * ih;
    }

    // @@ The implementation in nvmath.h should be equivalent.
    static inline int iround(float f)
    {
        // @@ Optimize this.
        return int(floorf(f+0.5f));
        //return int(round(f));
        //return int(f);
    }

    /// A triangle vertex. 
    struct Vertex
    {
        Vector2 pos;	// Position.
        Vector3 tex;	// Texcoord. (Barycentric coordinate)
    };


    /// A triangle for rasterization.
    struct Triangle
    {
        Triangle(Vector2::Arg v0, Vector2::Arg v1, Vector2::Arg v2, Vector3::Arg t0, Vector3::Arg t1, Vector3::Arg t2);

        bool computeDeltas();

        bool draw(const Vector2 & extents, bool enableScissors, SamplingCallback cb, void * param);
        bool drawAA(const Vector2 & extents, bool enableScissors, SamplingCallback cb, void * param);
        bool drawC(const Vector2 & extents, bool enableScissors, SamplingCallback cb, void * param);
        void flipBackface();
        void computeUnitInwardNormals();

        // Vertices.	
        Vector2 v1, v2, v3;
        Vector2 n1, n2, n3; // unit inward normals
        Vector3 t1, t2, t3;

        // Deltas.
        Vector3 dx, dy;

        float sign;
        bool valid;
    };


    /// Triangle ctor.
    Triangle::Triangle(Vector2::Arg v0, Vector2::Arg v1, Vector2::Arg v2, 
        Vector3::Arg t0, Vector3::Arg t1, Vector3::Arg t2)
    {
        // Init vertices.
        this->v1 = v0;
        this->v2 = v2;
        this->v3 = v1;

        // Set barycentric coordinates.
        this->t1 = t0;
        this->t2 = t2;
        this->t3 = t1;

        // make sure every triangle is front facing.
        flipBackface();

        // Compute deltas.
        valid = computeDeltas();

        computeUnitInwardNormals();
    }


    /// Compute texture space deltas.
    /// This method takes two edge vectors that form a basis, determines the 
    /// coordinates of the canonic vectors in that basis, and computes the 
    /// texture gradient that corresponds to those vectors.
    bool Triangle::computeDeltas()
    {
        Vector2 e0 = v3 - v1;
        Vector2 e1 = v2 - v1;

        Vector3 de0 = t3 - t1;
        Vector3 de1 = t2 - t1;

        float denom = 1.0f / (e0.y * e1.x - e1.y * e0.x);
        if (!isFinite(denom)) {
            return false;
        }

        float lambda1 = - e1.y * denom;
        float lambda2 = e0.y * denom;
        float lambda3 = e1.x * denom;
        float lambda4 = - e0.x * denom;

        dx = de0 * lambda1 + de1 * lambda2;
        dy = de0 * lambda3 + de1 * lambda4;

        return true;
    }

    // compute unit inward normals for each edge.
    void Triangle::computeUnitInwardNormals()
    {
        n1 = v1 - v2; n1 = Vector2(-n1.y, n1.x); n1 = n1 * (1.0f/sqrtf(n1.x*n1.x + n1.y*n1.y));
        n2 = v2 - v3; n2 = Vector2(-n2.y, n2.x); n2 = n2 * (1.0f/sqrtf(n2.x*n2.x + n2.y*n2.y));
        n3 = v3 - v1; n3 = Vector2(-n3.y, n3.x); n3 = n3 * (1.0f/sqrtf(n3.x*n3.x + n3.y*n3.y));
    }

    void Triangle::flipBackface()
    {
        // check if triangle is backfacing, if so, swap two vertices
        if ( ((v3.x-v1.x)*(v2.y-v1.y) - (v3.y-v1.y)*(v2.x-v1.x)) < 0 ) {
            Vector2 hv=v1; v1=v2; v2=hv; // swap pos
            Vector3 ht=t1; t1=t2; t2=ht; // swap tex
        }
    }

    bool Triangle::draw(const Vector2 & extents, bool enableScissors, SamplingCallback cb, void * param)
    {
        // 28.4 fixed-point coordinates
        const int Y1 = iround(16.0f * v1.y);
        const int Y2 = iround(16.0f * v2.y);
        const int Y3 = iround(16.0f * v3.y);

        const int X1 = iround(16.0f * v1.x);
        const int X2 = iround(16.0f * v2.x);
        const int X3 = iround(16.0f * v3.x);

        // Deltas
        const int DX12 = X1 - X2;
        const int DX23 = X2 - X3;
        const int DX31 = X3 - X1;

        const int DY12 = Y1 - Y2;
        const int DY23 = Y2 - Y3;
        const int DY31 = Y3 - Y1;

        // Fixed-point deltas
        const int FDX12 = DX12 << 4;
        const int FDX23 = DX23 << 4;
        const int FDX31 = DX31 << 4;

        const int FDY12 = DY12 << 4;
        const int FDY23 = DY23 << 4;
        const int FDY31 = DY31 << 4;

        int minx, miny, maxx, maxy;
        if (enableScissors) {
            int frustumX0 =  0 << 4;
            int frustumY0 =  0 << 4;
            int frustumX1 =  (int)extents.x << 4;
            int frustumY1 =  (int)extents.y << 4;

            // Bounding rectangle
            minx = (nv::max(min3(X1, X2, X3), frustumX0) + 0xF) >> 4;
            miny = (nv::max(min3(Y1, Y2, Y3), frustumY0) + 0xF) >> 4;
            maxx = (nv::min(max3(X1, X2, X3), frustumX1) + 0xF) >> 4;
            maxy = (nv::min(max3(Y1, Y2, Y3), frustumY1) + 0xF) >> 4;
        }
        else {
            // Bounding rectangle
            minx = (min3(X1, X2, X3) + 0xF) >> 4;
            miny = (min3(Y1, Y2, Y3) + 0xF) >> 4;
            maxx = (max3(X1, X2, X3) + 0xF) >> 4;
            maxy = (max3(Y1, Y2, Y3) + 0xF) >> 4;
        }

        // Block size, standard 8x8 (must be power of two)
        const int q = 8;

        // @@ This won't work when minx,miny are negative. This code path is not used. Leaving as is for now.
        nvCheck(minx >= 0);
        nvCheck(miny >= 0);

        // Start in corner of 8x8 block
        minx &= ~(q - 1);
        miny &= ~(q - 1);

        // Half-edge constants
        int C1 = DY12 * X1 - DX12 * Y1;
        int C2 = DY23 * X2 - DX23 * Y2;
        int C3 = DY31 * X3 - DX31 * Y3;

        // Correct for fill convention
        if(DY12 < 0 || (DY12 == 0 && DX12 > 0)) C1++;
        if(DY23 < 0 || (DY23 == 0 && DX23 > 0)) C2++;
        if(DY31 < 0 || (DY31 == 0 && DX31 > 0)) C3++;

        // Loop through blocks
        for(int y = miny; y < maxy; y += q)
        {
            for(int x = minx; x < maxx; x += q)
            {
                // Corners of block
                int x0 = x << 4;
                int x1 = (x + q - 1) << 4;
                int y0 = y << 4;
                int y1 = (y + q - 1) << 4;

                // Evaluate half-space functions
                bool a00 = C1 + DX12 * y0 - DY12 * x0 > 0;
                bool a10 = C1 + DX12 * y0 - DY12 * x1 > 0;
                bool a01 = C1 + DX12 * y1 - DY12 * x0 > 0;
                bool a11 = C1 + DX12 * y1 - DY12 * x1 > 0;
                int a = (a00 << 0) | (a10 << 1) | (a01 << 2) | (a11 << 3);

                bool b00 = C2 + DX23 * y0 - DY23 * x0 > 0;
                bool b10 = C2 + DX23 * y0 - DY23 * x1 > 0;
                bool b01 = C2 + DX23 * y1 - DY23 * x0 > 0;
                bool b11 = C2 + DX23 * y1 - DY23 * x1 > 0;
                int b = (b00 << 0) | (b10 << 1) | (b01 << 2) | (b11 << 3);

                bool c00 = C3 + DX31 * y0 - DY31 * x0 > 0;
                bool c10 = C3 + DX31 * y0 - DY31 * x1 > 0;
                bool c01 = C3 + DX31 * y1 - DY31 * x0 > 0;
                bool c11 = C3 + DX31 * y1 - DY31 * x1 > 0;
                int c = (c00 << 0) | (c10 << 1) | (c01 << 2) | (c11 << 3);

                // Skip block when outside an edge
                if(a == 0x0 || b == 0x0 || c == 0x0) continue;		

                // Accept whole block when totally covered
                if(a == 0xF && b == 0xF && c == 0xF)
                {
                    Vector3 texRow = t1 + dy*(y0 - v1.y) + dx*(x0 - v1.x);

                    for(int iy = y; iy < y + q; iy++)
                    {
                        Vector3 tex = texRow;
                        for(int ix = x; ix < x + q; ix++)
                        {
                            //Vector3 tex = t1 + dx * (ix - v1.x) + dy * (iy - v1.y);
                            if (!cb(param, ix, iy, tex, dx, dy, 1.0)) {
                                // early out.
                                return false;
                            }
                            tex += dx;
                        }
                        texRow += dy;
                    }
                }
                else // Partially covered block
                {
                    int CY1 = C1 + DX12 * y0 - DY12 * x0;
                    int CY2 = C2 + DX23 * y0 - DY23 * x0;
                    int CY3 = C3 + DX31 * y0 - DY31 * x0;
                    Vector3 texRow = t1 + dy*(y0 - v1.y) + dx*(x0 - v1.x);

                    for(int iy = y; iy < y + q; iy++)
                    {
                        int CX1 = CY1;
                        int CX2 = CY2;
                        int CX3 = CY3;
                        Vector3 tex = texRow;

                        for(int ix = x; ix < x + q; ix++)
                        {
                            if(CX1 > 0 && CX2 > 0 && CX3 > 0)
                            {
                                if (!cb(param, ix, iy, tex, dx, dy, 1.0))
                                {
                                    // early out.
                                    return false;
                                }
                            }

                            CX1 -= FDY12;
                            CX2 -= FDY23;
                            CX3 -= FDY31;
                            tex += dx;
                        }

                        CY1 += FDX12;
                        CY2 += FDX23;
                        CY3 += FDX31;
                        texRow += dy;
                    }
                }
            }
        }

        return true;
    }


#define PX_INSIDE    1.0f/sqrt(2.0f)
#define PX_OUTSIDE  -1.0f/sqrt(2.0f)

#define BK_SIZE 8
#define BK_INSIDE   sqrt(BK_SIZE*BK_SIZE/2.0f)
#define BK_OUTSIDE -sqrt(BK_SIZE*BK_SIZE/2.0f)

    // extents has to be multiple of BK_SIZE!!
    bool Triangle::drawAA(const Vector2 & extents, bool enableScissors, SamplingCallback cb, void * param)
    {
        float minx, miny, maxx, maxy;
        if (enableScissors) {
            // Bounding rectangle
            minx = floorf(max(min3(v1.x, v2.x, v3.x), 0.0f));
            miny = floorf(max(min3(v1.y, v2.y, v3.y), 0.0f));
            maxx = ceilf( min(max3(v1.x, v2.x, v3.x), extents.x-1.0f));
            maxy = ceilf( min(max3(v1.y, v2.y, v3.y), extents.y-1.0f));
        }
        else {
            // Bounding rectangle
            minx = floorf(min3(v1.x, v2.x, v3.x));
            miny = floorf(min3(v1.y, v2.y, v3.y));
            maxx = ceilf( max3(v1.x, v2.x, v3.x));
            maxy = ceilf( max3(v1.y, v2.y, v3.y));
        }

        // There's no reason to align the blocks to the viewport, instead we align them to the origin of the triangle bounds.
        minx = floorf(minx);
        miny = floorf(miny);
        //minx = (float)(((int)minx) & (~((int)BK_SIZE - 1))); // align to blocksize (we don't need to worry about blocks partially out of viewport)
        //miny = (float)(((int)miny) & (~((int)BK_SIZE - 1)));

        minx += 0.5; miny +=0.5;  // sampling at texel centers!
        maxx += 0.5; maxy +=0.5; 

        // Half-edge constants
        float C1 = n1.x * (-v1.x) + n1.y * (-v1.y);
        float C2 = n2.x * (-v2.x) + n2.y * (-v2.y);
        float C3 = n3.x * (-v3.x) + n3.y * (-v3.y);

        // Loop through blocks
        for(float y0 = miny; y0 <= maxy; y0 += BK_SIZE)
        {
            for(float x0 = minx; x0 <= maxx; x0 += BK_SIZE)
            {
                // Corners of block
                float xc = (x0 + (BK_SIZE-1)/2.0f);
                float yc = (y0 + (BK_SIZE-1)/2.0f);

                // Evaluate half-space functions
                float aC = C1 + n1.x * xc + n1.y * yc;
                float bC = C2 + n2.x * xc + n2.y * yc;
                float cC = C3 + n3.x * xc + n3.y * yc;

                // Skip block when outside an edge
                if( (aC <= BK_OUTSIDE) || (bC <= BK_OUTSIDE) || (cC <= BK_OUTSIDE) ) continue;

                // Accept whole block when totally covered
                if( (aC >= BK_INSIDE) && (bC >= BK_INSIDE) && (cC >= BK_INSIDE) )
                {
                    Vector3 texRow = t1 + dy*(y0 - v1.y) + dx*(x0 - v1.x);

                    for (float y = y0; y < y0 + BK_SIZE; y++)
                    {
                        Vector3 tex = texRow;
                        for(float x = x0; x < x0 + BK_SIZE; x++)
                        {
                            if (!cb(param, (int)x, (int)y, tex, dx, dy, 1.0f))
                            {
                                return false;
                            }
                            tex += dx;
                        }
                        texRow += dy;
                    }
                }
                else // Partially covered block
                {
                    float CY1 = C1 + n1.x * x0 + n1.y * y0;
                    float CY2 = C2 + n2.x * x0 + n2.y * y0;
                    float CY3 = C3 + n3.x * x0 + n3.y * y0;
                    Vector3 texRow = t1 + dy*(y0 - v1.y) + dx*(x0 - v1.x);	                  	

                    for(float y = y0; y < y0 + BK_SIZE; y++) // @@ This is not clipping to scissor rectangle correctly.
                    {
                        float CX1 = CY1;
                        float CX2 = CY2;
                        float CX3 = CY3;
                        Vector3 tex = texRow;

                        for (float x = x0; x < x0 + BK_SIZE; x++)   // @@ This is not clipping to scissor rectangle correctly.
                        {
                            if (CX1 >= PX_INSIDE && CX2 >= PX_INSIDE && CX3 >= PX_INSIDE) 
                            {
                                // pixel completely covered
                                Vector3 tex = t1 + dx * (x - v1.x) + dy * (y - v1.y);
                                if (!cb(param, (int)x, (int)y, tex, dx, dy, 1.0f))
                                {
                                    return false;
                                }
                            }
                            else if ((CX1 >= PX_OUTSIDE) && (CX2 >= PX_OUTSIDE) && (CX3 >= PX_OUTSIDE))
                            {
                                // triangle partially covers pixel. do clipping.
                                ClippedTriangle ct(v1-Vector2(x,y), v2-Vector2(x,y), v3-Vector2(x,y));
                                ct.clipAABox(-0.5, -0.5, 0.5, 0.5);
                                Vector2 centroid = ct.centroid();
                                float area = ct.area();
                                if (area > 0.0f)
                                {
                                    Vector3 texCent = tex - dx*centroid.x - dy*centroid.y;
                                    //nvCheck(texCent.x >= -0.1f && texCent.x <= 1.1f); // @@ Centroid is not very exact...
                                    //nvCheck(texCent.y >= -0.1f && texCent.y <= 1.1f);
                                    //nvCheck(texCent.z >= -0.1f && texCent.z <= 1.1f);
                                    //Vector3 texCent2 = t1 + dx * (x - v1.x) + dy * (y - v1.y);
                                    if (!cb(param, (int)x, (int)y, texCent, dx, dy, area))
                                    {
                                        return false;
                                    }
                                }
                            }

                            CX1 += n1.x;
                            CX2 += n2.x;
                            CX3 += n3.x;
                            tex += dx;
                        }

                        CY1 += n1.y;
                        CY2 += n2.y;
                        CY3 += n3.y;
                        texRow += dy;
                    }
                }
            }
        }

        return true;
    }

} // namespace


/// Process the given triangle.
bool nv::Raster::drawTriangle(Mode mode, Vector2::Arg extents, bool enableScissors, const Vector2 v[3], SamplingCallback cb, void * param)
{
    Triangle tri(v[0], v[1], v[2], Vector3(1, 0, 0), Vector3(0, 1, 0), Vector3(0, 0, 1));
    
    // @@ It would be nice to have a conservative drawing mode that enlarges the triangle extents by one texel and is able to handle degenerate triangles.
    // @@ Maybe the simplest thing to do would be raster triangle edges.

    if (tri.valid) {
        if (mode == Mode_Antialiased) {
            return tri.drawAA(extents, enableScissors, cb, param);
        } 
        if (mode == Mode_Nearest) {
            return tri.draw(extents, enableScissors, cb, param);
        }
    }

    return true;
}

inline static float triangleArea(Vector2::Arg v1, Vector2::Arg v2, Vector2::Arg v3)
{
    return 0.5f * (v3.x * v1.y + v1.x * v2.y + v2.x * v3.y - v2.x * v1.y - v3.x * v2.y - v1.x * v3.y);
}

/// Process the given quad.
bool nv::Raster::drawQuad(Mode mode, Vector2::Arg extents, bool enableScissors, const Vector2 v[4], SamplingCallback cb, void * param)
{
    bool sign0 = triangleArea(v[0], v[1], v[2]) > 0.0f;
    bool sign1 = triangleArea(v[0], v[2], v[3]) > 0.0f;

    // Divide the quad into two non overlapping triangles.
    if (sign0 == sign1) {
        Triangle tri0(v[0], v[1], v[2], Vector3(0,0,0), Vector3(1,0,0), Vector3(1,1,0));
        Triangle tri1(v[0], v[2], v[3], Vector3(0,0,0), Vector3(1,1,0), Vector3(0,1,0));

        if (tri0.valid && tri1.valid) {
            if (mode == Mode_Antialiased) {
                return tri0.drawAA(extents, enableScissors, cb, param) && tri1.drawAA(extents, enableScissors, cb, param);
            } else {
                return tri0.draw(extents, enableScissors, cb, param) && tri1.draw(extents, enableScissors, cb, param);
            }
        }
    }
    else
    {
        Triangle tri0(v[0], v[1], v[3], Vector3(0,0,0), Vector3(1,0,0), Vector3(0,1,0));
        Triangle tri1(v[1], v[2], v[3], Vector3(1,0,0), Vector3(1,1,0), Vector3(0,1,0));

        if (tri0.valid && tri1.valid) {
            if (mode == Mode_Antialiased) {
                return tri0.drawAA(extents, enableScissors, cb, param) && tri1.drawAA(extents, enableScissors, cb, param);
            } else {
                return tri0.draw(extents, enableScissors, cb, param) && tri1.draw(extents, enableScissors, cb, param);
            }
        }
    }

    return true;
}


static bool drawPoint(const Vector2 & p, const Vector2 v[2], LineSamplingCallback cb, void * param) {

    int x = ftoi_round(p.x);
    int y = ftoi_round(p.y);
    Vector2 ip = Vector2(float(x) + 0.5f, float(y) + 0.5f);

    float t;

    // Return minimum distance between line segment vw and point p
    Vector2 dv = v[1] - v[0];
    const float l2 = nv::lengthSquared(dv);  // i.e. |w-v|^2 -  avoid a sqrt
    if (l2 == 0.0) {
        t = 0;                  // v0 == v1 case
    }
    else {
        // Consider the line extending the segment, parameterized as v + t (w - v).
        // We find projection of point p onto the line. 
        // It falls where t = [(p-v) . (w-v)] / |w-v|^2
        t = dot(ip - v[0], dv) / l2;
        if (t < 0.0) {
            t = 0;                      // Beyond the 'v0' end of the segment
        }
        else if (t > 1.0) {
            t = 1;                      // Beyond the 'v1' end of the segment
        }
    }
    
    Vector2 projection = v[0] + t * dv; // Projection falls on the segment

    float d = distance(ip, projection);

    return cb(param, x, y, t, saturate(1-d));
}


void nv::Raster::drawLine(bool antialias, Vector2::Arg extents, bool enableScissors, const Vector2 v[2], LineSamplingCallback cb, void * param)
{
    nvCheck(antialias == true);         // @@ Not implemented.
    //nvCheck(enableScissors == false); // @@ Not implemented.

    // Very crappy DDA implementation.

    Vector2 p = v[0];
    Vector2 dp, dpdy;

    float dx = v[1].x - v[0].x;
    float dy = v[1].y - v[0].y;
    int n;

    // Degenerate line.
    if (dx == 0 && dy == 0) return;

    if (fabsf(dx) >= fabsf(dy)) {
        n = iround(fabsf(dx));
        dp.x = dx / fabsf(dx);
        dp.y = dy / fabsf(dx);
        nvDebugCheck(fabsf(dp.y) <= 1.0f);
        dpdy.x = 0;
        dpdy.y = 1;
    }
    else {
        n = iround(fabs(dy));
        dp.x = dx / fabsf(dy);
        dp.y = dy / fabsf(dy);
        nvDebugCheck(fabsf(dp.x) <= 1.0f);
        dpdy.x = 1;
        dpdy.y = 0;
    }

    for (int i = 0; i <= n; i++) {
        drawPoint(p, v, cb, param);
        drawPoint(p + dpdy, v, cb, param);
        drawPoint(p - dpdy, v, cb, param);
        p += dp;
    }
}


// Draw vertical or horizontal segments. For degenerate triangles.
/*bool nv::Raster::drawSegment(Vector2::Arg extents, bool enableScissors, const Vector2 v[2], LineSamplingCallback cb, void * param)
{
    nvCheck(enableScissors == false);

    
    if (v[0].x == v[1].x) {         // Vertical segment.
        
    }
    else if (v[0].y == v[1].y) {    // Horizontal segment.
        int y = ftoi_round(v[0].y);
        int x0 = ftoi_floor(v[0].x);
        int x1 = ftoi_floor(v[0].x);

        for (int x = x0; x <= x1; x++) {

            cb(param, x, y, t, 
        }
    }

    return false; // Not a valid segment.
}
*/