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/* ResidualVM - A 3D game interpreter
*
* ResidualVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the AUTHORS
* file distributed with this source distribution.
*
* 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 2
* of the License, or (at your option) 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 should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
*/
/*
* This file is based on, or a modified version of code from TinyGL (C) 1997-1998 Fabrice Bellard,
* which is licensed under the zlib-license (see LICENSE).
* It also has modifications by the ResidualVM-team, which are covered under the GPLv2 (or later).
*/
#include "graphics/tinygl/zbuffer.h"
namespace TinyGL {
template <bool kDepthWrite>
FORCEINLINE void FrameBuffer::putPixel(unsigned int pixelOffset, int color, int x, int y, unsigned int z) {
if (_enableScissor)
putPixel<kDepthWrite, true>(pixelOffset, color, x, y, z);
else
putPixel<kDepthWrite, false>(pixelOffset, color, x, y, z);
}
template <bool kDepthWrite, bool kEnableScissor>
FORCEINLINE void FrameBuffer::putPixel(unsigned int pixelOffset, int color, int x, int y, unsigned int z) {
if (kEnableScissor && scissorPixel(x, y)) {
return;
}
unsigned int *pz = _zbuf + pixelOffset;
if (compareDepth(z, *pz)) {
writePixel<true, true, kDepthWrite>(pixelOffset, color, z);
}
}
template <bool kEnableScissor>
FORCEINLINE void FrameBuffer::putPixel(unsigned int pixelOffset, int color, int x, int y) {
if (kEnableScissor && scissorPixel(x, y)) {
return;
}
writePixel<true, true>(pixelOffset, color);
}
template <bool kInterpRGB, bool kInterpZ, bool kDepthWrite>
FORCEINLINE void FrameBuffer::drawLine(const ZBufferPoint *p1, const ZBufferPoint *p2) {
if (_enableScissor)
drawLine<kInterpRGB, kInterpZ, kDepthWrite, true>(p1, p2);
else
drawLine<kInterpRGB, kInterpZ, kDepthWrite, false>(p1, p2);
}
template <bool kInterpRGB, bool kInterpZ, bool kDepthWrite, bool kEnableScissor>
void FrameBuffer::drawLine(const ZBufferPoint *p1, const ZBufferPoint *p2) {
// Based on Bresenham's line algorithm, as implemented in
// https://rosettacode.org/wiki/Bitmap/Bresenham%27s_line_algorithm#C
// with a loop exit condition based on the (unidimensional) taxicab
// distance between p1 and p2 (which is cheap to compute and
// rounding-error-free) so that interpolations are possible without
// code duplication.
// Where we are in unidimensional framebuffer coordinate
unsigned int pixelOffset = p1->y * xsize + p1->x;
// and in 2d
int x = p1->x;
int y = p1->y;
// How to move on each axis, in both coordinates systems
const int dx = abs(p2->x - p1->x);
const int inc_x = p1->x < p2->x ? 1 : -1;
const int dy = abs(p2->y - p1->y);
const int inc_y = p1->y < p2->y ? 1 : -1;
const int inc_y_pixel = p1->y < p2->y ? xsize : -xsize;
// When to move on each axis
int err = (dx > dy ? dx : -dy) / 2;
int e2;
// How many moves
int n = dx > dy ? dx : dy;
// kInterpZ
unsigned int z;
int sz;
// kInterpRGB
int r = p1->r >> (ZB_POINT_RED_BITS - 8);
int g = p1->g >> (ZB_POINT_GREEN_BITS - 8);
int b = p1->b >> (ZB_POINT_BLUE_BITS - 8);
int color = RGB_TO_PIXEL(r, g, b);
int sr, sg, sb;
if (kInterpZ) {
sz = (p2->z - p1->z) / n;
z = p1->z;
}
if (kInterpRGB) {
sr = ((p2->r - p1->r) / n) >> (ZB_POINT_RED_BITS - 8);
sg = ((p2->g - p1->g) / n) >> (ZB_POINT_GREEN_BITS - 8);
sb = ((p2->b - p1->b) / n) >> (ZB_POINT_BLUE_BITS - 8);
}
while (n--) {
if (kInterpZ)
putPixel<kDepthWrite, kEnableScissor>(pixelOffset, color, x, y, z);
else
putPixel<kEnableScissor>(pixelOffset, color, x, y);
e2 = err;
if (e2 > -dx) {
err -= dy;
pixelOffset += inc_x;
x += inc_x;
}
if (e2 < dy) {
err += dx;
pixelOffset += inc_y_pixel;
y += inc_y;
}
if (kInterpZ)
z += sz;
if (kInterpRGB) {
r += sr;
g += sg;
b += sb;
color = RGB_TO_PIXEL(r, g, b);
}
}
}
void FrameBuffer::plot(ZBufferPoint *p) {
const unsigned int pixelOffset = p->y * xsize + p->x;
const int col = RGB_TO_PIXEL(p->r, p->g, p->b);
const unsigned int z = p->z;
if (_depthWrite && _depthTestEnabled)
putPixel<true>(pixelOffset, col, p->x, p->y, z);
else
putPixel<false>(pixelOffset, col, p->x, p->y, z);
}
void FrameBuffer::fillLineFlatZ(ZBufferPoint *p1, ZBufferPoint *p2) {
if (_depthWrite && _depthTestEnabled)
drawLine<false, true, true>(p1, p2);
else
drawLine<false, true, false>(p1, p2);
}
// line with color interpolation
void FrameBuffer::fillLineInterpZ(ZBufferPoint *p1, ZBufferPoint *p2) {
if (_depthWrite && _depthTestEnabled)
drawLine<true, true, true>(p1, p2);
else
drawLine<true, true, false>(p1, p2);
}
// no Z interpolation
void FrameBuffer::fillLineFlat(ZBufferPoint *p1, ZBufferPoint *p2) {
if (_depthWrite && _depthTestEnabled)
drawLine<false, false, true>(p1, p2);
else
drawLine<false, false, false>(p1, p2);
}
void FrameBuffer::fillLineInterp(ZBufferPoint *p1, ZBufferPoint *p2) {
if (_depthWrite && _depthTestEnabled)
drawLine<false, true, true>(p1, p2);
else
drawLine<false, true, false>(p1, p2);
}
void FrameBuffer::fillLineZ(ZBufferPoint *p1, ZBufferPoint *p2) {
// choose if the line should have its color interpolated or not
if (p1->r == p2->r && p1->g == p2->g && p1->b == p2->b)
fillLineFlatZ(p1, p2);
else
fillLineInterpZ(p1, p2);
}
void FrameBuffer::fillLine(ZBufferPoint *p1, ZBufferPoint *p2) {
// choose if the line should have its color interpolated or not
if (p1->r == p2->r && p1->g == p2->g && p1->b == p2->b)
fillLineFlat(p1, p2);
else
fillLineInterp(p1, p2);
}
} // end of namespace TinyGL
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