libcaca/caca/triangle.c

/*
 *  libcaca       Colour ASCII-Art library
 *  Copyright (c) 2002-2006 Sam Hocevar <sam@zoy.org>
 *                All Rights Reserved
 *
 *  $Id$
 *
 *  This library is free software. It comes without any warranty, to
 *  the extent permitted by applicable law. You can redistribute it
 *  and/or modify it under the terms of the Do What The Fuck You Want
 *  To Public License, Version 2, as published by Sam Hocevar. See
 *  http://sam.zoy.org/wtfpl/COPYING for more details.
 */

/*
 *  This file contains triangle drawing functions, both filled and outline.
 */

#include "config.h"

#if !defined(__KERNEL__)
#   include <stdlib.h>
#endif

#include "caca.h"
#include "caca_internals.h"

/** \brief Draw a triangle on the canvas using the given character.
 *
 *  This function never fails.
 *
 *  \param cv The handle to the libcaca canvas.
 *  \param x1 X coordinate of the first point.
 *  \param y1 Y coordinate of the first point.
 *  \param x2 X coordinate of the second point.
 *  \param y2 Y coordinate of the second point.
 *  \param x3 X coordinate of the third point.
 *  \param y3 Y coordinate of the third point.
 *  \param ch UTF-32 character to be used to draw the triangle outline.
 *  \return This function always returns 0.
 */
int caca_draw_triangle(caca_canvas_t *cv, int x1, int y1, int x2, int y2,
                        int x3, int y3, uint32_t ch)
{
    caca_draw_line(cv, x1, y1, x2, y2, ch);
    caca_draw_line(cv, x2, y2, x3, y3, ch);
    caca_draw_line(cv, x3, y3, x1, y1, ch);

    return 0;
}

/** \brief Draw a thin triangle on the canvas.
 *
 *  This function never fails.
 *
 *  \param cv The handle to the libcaca canvas.
 *  \param x1 X coordinate of the first point.
 *  \param y1 Y coordinate of the first point.
 *  \param x2 X coordinate of the second point.
 *  \param y2 Y coordinate of the second point.
 *  \param x3 X coordinate of the third point.
 *  \param y3 Y coordinate of the third point.
 *  \return This function always returns 0.
 */
int caca_draw_thin_triangle(caca_canvas_t *cv, int x1, int y1,
                             int x2, int y2, int x3, int y3)
{
    caca_draw_thin_line(cv, x1, y1, x2, y2);
    caca_draw_thin_line(cv, x2, y2, x3, y3);
    caca_draw_thin_line(cv, x3, y3, x1, y1);

    return 0;
}

/** \brief Fill a triangle on the canvas using the given character.
 *
 *  This function never fails.
 *
 *  \param cv The handle to the libcaca canvas.
 *  \param x1 X coordinate of the first point.
 *  \param y1 Y coordinate of the first point.
 *  \param x2 X coordinate of the second point.
 *  \param y2 Y coordinate of the second point.
 *  \param x3 X coordinate of the third point.
 *  \param y3 Y coordinate of the third point.
 *  \param ch UTF-32 character to be used to fill the triangle.
 *  \return This function always returns 0.
 */
int caca_fill_triangle(caca_canvas_t *cv, int x1, int y1, int x2, int y2,
                        int x3, int y3, uint32_t ch)
{
    int x, y, xmin, xmax, ymin, ymax;
    int xx1, xx2, xa, xb, sl21, sl31, sl32;

    /* Bubble-sort y1 <= y2 <= y3 */
    if(y1 > y2)
        return caca_fill_triangle(cv, x2, y2, x1, y1, x3, y3, ch);

    if(y2 > y3)
        return caca_fill_triangle(cv, x1, y1, x3, y3, x2, y2, ch);

    /* Compute slopes and promote precision */
    sl21 = (y2 == y1) ? 0 : (x2 - x1) * 0x10000 / (y2 - y1);
    sl31 = (y3 == y1) ? 0 : (x3 - x1) * 0x10000 / (y3 - y1);
    sl32 = (y3 == y2) ? 0 : (x3 - x2) * 0x10000 / (y3 - y2);

    x1 *= 0x10000;
    x2 *= 0x10000;
    x3 *= 0x10000;

    ymin = y1 < 0 ? 0 : y1;
    ymax = y3 + 1 < cv->height ? y3 + 1 : cv->height;

    if(ymin < y2)
    {
        xa = x1 + sl21 * (ymin - y1);
        xb = x1 + sl31 * (ymin - y1);
    }
    else if(ymin == y2)
    {
        xa = x2;
        xb = (y1 == y3) ? x3 : x1 + sl31 * (ymin - y1);
    }
    else /* (ymin > y2) */
    {
        xa = x3 + sl32 * (ymin - y3);
        xb = x3 + sl31 * (ymin - y3);
    }

    /* Rasterize our triangle */
    for(y = ymin; y < ymax; y++)
    {
        /* Rescale xa and xb, recentering the division */
        if(xa < xb)
        {
            xx1 = (xa + 0x800) / 0x10000;
            xx2 = (xb + 0x801) / 0x10000;
        }
        else
        {
            xx1 = (xb + 0x800) / 0x10000;
            xx2 = (xa + 0x801) / 0x10000;
        }

        xmin = xx1 < 0 ? 0 : xx1;
        xmax = xx2 + 1 < cv->width ? xx2 + 1 : cv->width;

        for(x = xmin; x < xmax; x++)
            caca_put_char(cv, x, y, ch);

        xa += y < y2 ? sl21 : sl32;
        xb += sl31;
    }

    return 0;
}

/* This function actually renders the triangle, 
 * but is not exported due to sam's pedantic will. */
static int caca_fill_triangle_textured_l(caca_canvas_t *cv,
                                int x1, int y1,
                                int x2, int y2,
                       			int x3, int y3,
                                caca_canvas_t *tex,
                                float u1, float v1,
                                float u2, float v2,
                       			float u3, float v3)
                                
{
    uint32_t savedattr;

    #define SWAP_F(a, b) {float c = a; a = b; b = c; }
    
    /* (very) Naive and 
     * (very) float-based affine and
     * (very) non-clipped and
     * (very) non-corrected triangle mapper 
     *
     * Accepts arbitrary texture sizes
     * Coordinates clamped to [0.0 - 1.0] (no repeat)
     */
    if(!cv || !tex) return -1;

    /* Bubble-sort y1 <= y2 <= y3 */
    if(y1 > y2)
        return caca_fill_triangle_textured_l(cv, 
                                             x2, y2, x1, y1, x3, y3,
                                             tex,
                                             u2, v2, u1, v1, u3, v3);
    if(y2 > y3) 
        return caca_fill_triangle_textured_l(cv, 
                                             x1, y1, x3, y3, x2, y2,
                                             tex,
                                             u1, v1, u3, v3, u2, v2);

    savedattr = caca_get_attr(cv, -1, -1);

    /* Clip texture coordinates */
    if(u1<0.0f) u1 = 0.0f; if(v1<0.0f) v1 = 0.0f;
    if(u2<0.0f) u2 = 0.0f; if(v2<0.0f) v2 = 0.0f;
    if(u3<0.0f) u3 = 0.0f; if(v3<0.0f) v3 = 0.0f;
    if(u1>1.0f) u1 = 1.0f; if(v1>1.0f) v1 = 1.0f;
    if(u2>1.0f) u2 = 1.0f; if(v2>1.0f) v2 = 1.0f;
    if(u3>1.0f) u3 = 1.0f; if(v3>1.0f) v3 = 1.0f;
    
    /* Convert relative tex coordinates to absolute */
    int tw = caca_get_canvas_width(tex);
    int th = caca_get_canvas_height(tex);
    
    u1*=(float)tw; u2*=(float)tw; u3*=(float)tw;
    v1*=(float)th; v2*=(float)th; v3*=(float)th;
    
    int x, y;
    float y2y1 = y2-y1;
    float y3y1 = y3-y1;
    float y3y2 = y3-y2;
    
    /* Compute slopes, making sure we don't divide by zero */
    /* (in this case, we don't need the value anyway) */
    /* FIXME : only compute needed slopes */
    float sl12 = ((float)x2 - x1) / (y2y1==0?1:y2y1);
    float sl13 = ((float)x3 - x1) / (y3y1==0?1:y3y1);
    float sl23 = ((float)x3 - x2) / (y3y2==0?1:y3y2);
    
    float usl12 = (u2 - u1) / (y2y1==0?1:y2y1);
    float usl13 = (u3 - u1) / (y3y1==0?1:y3y1);
    float usl23 = (u3 - u2) / (y3y2==0?1:y3y2);
    float vsl12 = (v2 - v1) / (y2y1==0?1:y2y1);
    float vsl13 = (v3 - v1) / (y3y1==0?1:y3y1);
    float vsl23 = (v3 - v2) / (y3y2==0?1:y3y2);
    
    float xa = (float) x1, xb = (float) x1;
    float ua = u1, ub = u1;
    float va = v1, vb = v1;
    float u, v;
    
    int s = 0;
    
    /* Top */
    for(y = y1 ; y < y2; y++)
    {
        
        if(xb < xa) {
            SWAP_F(xb, xa);   
            SWAP_F(sl13, sl12);
            SWAP_F(ua, ub);
            SWAP_F(va, vb);            
            SWAP_F(usl13, usl12);
            SWAP_F(vsl13, vsl12);
            s=1;
        }
        
        float tus = (ub - ua) / (xb - xa);
        float tvs = (vb - va) / (xb - xa);
        v = va; u = ua;
        
        /* scanline */
        for(x = xa ; x < xb; x++)
        {
            u+=tus;
            v+=tvs;
            /* FIXME: use caca_get_canvas_attrs / caca_get_canvas_chars  */
            uint32_t attr = caca_get_attr(tex, u, v);
            uint32_t c    = caca_get_char(tex, u, v);
            caca_set_attr(cv, attr);
            caca_put_char(cv, x, y, c);
        }
        
        xa+=sl13;
        xb+=sl12;
        
        ua+=usl13; va+=vsl13;
        ub+=usl12; vb+=vsl12;
    }
    
    if(s)
    {
        SWAP_F(xb, xa);
        SWAP_F(sl13, sl12);
        SWAP_F(ua, ub);
        SWAP_F(va, vb);
        SWAP_F(usl13, usl12);
        SWAP_F(vsl13, vsl12);
    }
    
    
    /* Bottom */
    xb = (float) x2;

    /* These variables are set by 'top' routine 
     * and are in an incorrect state if we only draw the bottom part
     */
   	if(y1 == y2) {
        ua = u1;
        ub = u2;
        va = v1;
        vb = v2;
    }
    
    for(y = y2 ; y < y3; y++)
    {
        if(xb <= xa)
        {
            SWAP_F(xb, xa);
            SWAP_F(sl13, sl23);
            SWAP_F(ua, ub);
            SWAP_F(va, vb);
            SWAP_F(usl13, usl23);
            SWAP_F(vsl13, vsl23);
        } 
        
        float tus = (ub - ua) / ((float)xb - xa);
        float tvs = (vb - va) / ((float)xb - xa);
        u = ua; v = va;
        
        /* scanline */
        for(x = xa ; x < xb; x++)
        {    
            u+=tus;
            v+=tvs;
            /* FIXME, can be heavily optimised  */
            uint32_t attr = caca_get_attr(tex, u, v);
            uint32_t c    = caca_get_char(tex, u, v);
            caca_set_attr(cv, attr);
            caca_put_char(cv, x, y, c);
        }

        xa+=sl13;
        xb+=sl23;
        
        ua+=usl13; va+=vsl13;
        ub+=usl23; vb+=vsl23;
    }

    caca_set_attr(cv, savedattr);

    return 0;
}

/** \brief Fill a triangle on the canvas using an arbitrary-sized texture.
 *
 *  This function fails if one or both the canvas are missing
 *
 *  \param cv     The handle to the libcaca canvas.
 *  \param coords The coordinates of the triangle (3{x,y})
 *  \param tex    The handle of the canvas texture.
 *  \param uv     The coordinates of the texture (3{u,v})
 *  \return This function return 0 if ok, -1 if canvas or texture are missing.
 */
int caca_fill_triangle_textured(caca_canvas_t *cv,
                                int coords[6],
                                caca_canvas_t *tex,
                                float uv[6]) {
    
    return caca_fill_triangle_textured_l(cv,
                                         coords[0], coords[1],
                                         coords[2], coords[3],
                                         coords[4], coords[5],
                                         tex,
                                         uv[0],     uv[1],
                                         uv[2],     uv[3],
                                         uv[4],     uv[5]);
}



/*
 * XXX: The following functions are aliases.
 */

int cucul_draw_triangle(cucul_canvas_t *, int, int, int, int, int,
                      int, uint32_t) CACA_ALIAS(caca_draw_triangle);
int cucul_draw_thin_triangle(cucul_canvas_t *, int, int, int, int,
                             int, int) CACA_ALIAS(caca_draw_thin_triangle);
int cucul_fill_triangle(cucul_canvas_t *, int, int, int, int, int,
                        int, uint32_t) CACA_ALIAS(caca_fill_triangle);