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/**
** sipp - SImple Polygon Processor
**
** A general 3d graphic package
**
** Copyright Equivalent Software HB 1992
**
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 1, or any later version.
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
** GNU General Public License for more details.
** You can receive a copy of the GNU General Public License from the
** Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
**/
/**
** wood.c - Wood shader: Simulates wood using multiple skewed "cylinders"
** distorted with noise and turbulence.
**/
#include <math.h>
#include <stdio.h>
#include <sipp.h>
#include <noise.h>
#include <shaders.h>
#define BOARDSIZE 45.0 /* "Log" or "board" size in texture coordinates */
void
wood_shader(pos, normal, texture, view_vec, lights, wd, color, opacity)
Vector *pos;
Vector *normal;
Vector *texture;
Vector *view_vec;
Lightsource *lights;
Wood_desc *wd;
Color *color;
Color *opacity;
{
Vector tpos;
Vector tmp;
Surf_desc surface;
double chaos;
double val;
double val2;
double skewoff;
double t;
double rad;
if (!noise_ready) {
noise_init();
}
/*
* Scale the texture coordinates.
*/
VecScalMul(tpos, wd->scale, *texture);
/*
* Get some noise values. Drag out the texture in
* the direction of the "stem" of the fictive tree, the
* pattern should vary less along that direction.
*/
tpos.x *= 0.08;
chaos = turbulence(&tpos, 5) * 0.5;
val2 = noise(&tpos);
/*
* Make the pattern "semi"-periodic so it looks as if
* a new board is used at regular intervals
*/
if (tpos.z > 0.0) {
tmp.z = floor((tpos.z + BOARDSIZE * 0.5) / BOARDSIZE);
tpos.z -= tmp.z * BOARDSIZE;
} else {
tmp.z = floor((BOARDSIZE * 0.5 - tpos.z) / BOARDSIZE);
tpos.z += tmp.z * BOARDSIZE;
}
if (tpos.y > 0.0) {
tmp.y = floor((tpos.y + BOARDSIZE * 0.5) / BOARDSIZE);
tpos.y -= tmp.y * BOARDSIZE;
} else {
tmp.y = floor((BOARDSIZE * 0.5 - tpos.y) / BOARDSIZE);
tpos.y += tmp.y * BOARDSIZE;
}
/*
* Skew the "stem" a bit so the "cylinders" isn't perfectly
* symmertic about the x-axis. Skew the different "logs"
* slightly differently.
*/
tmp.x = 0.0;
skewoff = noise(&tmp);
tpos.z -= (0.05 + 0.03 * skewoff) * (texture->x * wd->scale - 2.0);
tpos.y -= (0.05 + 0.03 * skewoff) * (texture->x * wd->scale - 2.0);
/*
* Calculate the distance from the middle of the "stem" and
* distort this distance with the turbulence value.
*/
rad = sqrt(tpos.y * tpos.y + tpos.z * tpos.z);
rad += chaos;
val = rad - floor(rad);
/*
* Choose a color dependent on the distorted distance.
*/
if (val < 0.1) {
surface.color.red = wd->base.red;
surface.color.grn = wd->base.grn;
surface.color.blu = wd->base.blu;
} else if (val < 0.9) {
t = 1.0 - pow(val / 0.8 - 0.1, 6.0);
surface.color.red = wd->ring.red + t * (wd->base.red
- wd->ring.red);
surface.color.grn = wd->ring.grn + t * (wd->base.grn
- wd->ring.grn);
surface.color.blu = wd->ring.blu + t * (wd->base.blu
- wd->ring.blu);
} else {
surface.color.red = wd->ring.red;
surface.color.grn = wd->ring.grn;
surface.color.blu = wd->ring.blu;
}
/*
* Add a little extra "noise" so the pattern doesn't get
* too regular, this could be small cracks, or other anomalies
* in the wood.
*/
if (val2 < 0.01 && val2 > 0.0) {
surface.color.red = wd->ring.red;
surface.color.grn = wd->ring.grn;
surface.color.blu = wd->ring.blu;
}
surface.ambient = wd->ambient;
surface.specular = wd->specular;
surface.c3 = wd->c3;
surface.opacity = wd->opacity;
basic_shader(pos, normal, texture, view_vec, lights, &surface,
color, opacity);
}
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