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2018-soft-3d-renderer
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Convert triangle rasterization to use barycentric

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master
Austin Morlan 4 years ago
parent d0041c77c4
commit 0c5cf83748
Signed by: austin
GPG Key ID: FD6B27654AF5E348
3 changed files with 61 additions and 194 deletions
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8
include/geometry.h
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@ -1,6 +1,7 @@
#ifndef GEOMETRY_H
#include "color.h"
#include "engine.h"
#include "point.h"
#include <cstdint>
#include <vector>
@ -77,11 +78,8 @@ struct Mesh
// PUBLIC FUNCTIONS
void FillTriangle(
uint32_t *buffer, int width,
float *zbuffer, uint32_t color,
float x0, float y0, float z0,
float x1, float y1, float z1,
float x2, float y2, float z2);
Engine_Buffer &buffer, ColorU32 &color,
Point &p0, Point &p1, Point &p2);
#define GEOMETRY_H

12
src/engine.cpp
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@ -50,9 +50,12 @@ void Engine_Render(Engine_Buffer &buffer, uint32_t input)
{
CheckInputs(input);
// Clear the z-buffer
unsigned long bufferSize = (unsigned long)(buffer.width * buffer.height);
memset(buffer.zbuffer, 0, bufferSize * sizeof(float));
// Local space to world space
Matrix tTranslate = Transform_Translate(
mesh.position.x, mesh.position.y, mesh.position.z);
@ -122,11 +125,10 @@ void Engine_Render(Engine_Buffer &buffer, uint32_t input)
unsigned int v2 = mesh.culledFaces[f].vertIndex[2];
FillTriangle(
buffer.buffer, buffer.width,
buffer.zbuffer, mesh.faces[f].color.u32,
mesh.vertsTransformed[v0].x, mesh.vertsTransformed[v0].y, mesh.vertsTransformed[v0].z,
mesh.vertsTransformed[v1].x, mesh.vertsTransformed[v1].y, mesh.vertsTransformed[v1].z,
mesh.vertsTransformed[v2].x, mesh.vertsTransformed[v2].y, mesh.vertsTransformed[v2].z);
buffer, mesh.faces[f].color,
mesh.vertsTransformed[v0],
mesh.vertsTransformed[v1],
mesh.vertsTransformed[v2]);
}
}

235
src/geometry.cpp
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@ -1,6 +1,8 @@
#include "color.h"
#include "engine.h"
#include "geometry.h"
#include "util.h"
#include <cstdio>
// MACROS
@ -10,215 +12,80 @@
}
// PRIVATE PROTOTYPES
static void FillTriangleFlatBottom(
uint32_t *buffer, int width,
float *zbuffer, uint32_t color,
float x0, float y0, float z0,
float x1, float y1, float z1,
float x2, float y2, float z2);
static void FillTriangleFlatTop(
uint32_t *buffer, int width,
float *zbuffer, uint32_t color,
float x0, float y0, float z0,
float x1, float y1, float z1,
float x2, float y2, float z2);
// PUBLIC FUNCTIONS
void FillTriangle(
uint32_t *buffer, int width,
float *zbuffer, uint32_t color,
float x0, float y0, float z0,
float x1, float y1, float z1,
float x2, float y2, float z2)
// STRUCTURES
struct BoundingBox
{
// Horizontal or vertical
if ((FLOAT_EQUAL(x0,x1) && FLOAT_EQUAL(x1, x2))
|| (FLOAT_EQUAL(y0, y1) && FLOAT_EQUAL(y1, y2)))
BoundingBox(Point &v0, Point &v1, Point &v2)
{
return;
}
yMin = MIN(v0.y, MIN(v1.y, v2.y));
yMax = MAX(v0.y, MAX(v1.y, v2.y));
// Sort in ascending Y order
float temp;
if (y0 > y1)
{
SWAP(x0, x1, temp);
SWAP(y0, y1, temp);
SWAP(z0, z1, temp);
xMin = MIN(v0.x, MIN(v1.x, v2.x));
xMax = MAX(v0.x, MAX(v1.x, v2.x));
}
if (y0 > y2)
{
SWAP(x0, x2, temp);
SWAP(y0, y2, temp);
SWAP(z0, z2, temp);
}
float yMin, yMax;
float xMin, xMax;
};
if (y1 > y2)
{
SWAP(x1, x2, temp);
SWAP(y1, y2, temp);
SWAP(z1, z2, temp);
}
static void ComputeBarycenter(float *w, Point &v0, Point &v1, Point &v2, Point &p)
{
float area = (v2.x - v0.x) * (v1.y - v0.y) - (v2.y - v0.y) * (v1.x - v0.x);
// Flat top triangle
if (FLOAT_EQUAL(y0, y1))
{
FillTriangleFlatTop(buffer, width, zbuffer, color, x0, y0, z0, x1, y1, z1, x2, y2, z2);
}
float result[3];
result[0] = (p.x - v1.x) * (v2.y - v1.y) - (p.y - v1.y) * (v2.x - v1.x);
result[1] = (p.x - v2.x) * (v0.y - v2.y) - (p.y - v2.y) * (v0.x - v2.x);
result[2] = (p.x - v0.x) * (v1.y - v0.y) - (p.y - v0.y) * (v1.x - v0.x);
// Flat bottom triangle
else if (FLOAT_EQUAL(y1, y2))
{
FillTriangleFlatBottom(buffer, width, zbuffer, color, x0, y0, z0, x1, y1, z1, x2, y2, z2);
}
result[0] /= area;
result[1] /= area;
result[2] /= area;
// Other - decompose into two triangles
else
{
// Calculate x coordinate at point of decomposition using intercept theorem
// New y is the same as y1
float x3 = x0 + (((y1 - y0) / (y2 - y0)) * (x2 - x0));
float y3 = y1;
float z3 = z1;
FillTriangleFlatBottom(buffer, width, zbuffer, color, x0, y0, z0, x1, y1, z1, x3, y3, z3);
FillTriangleFlatTop(buffer, width, zbuffer, color, x1, y1, z1, x3, y3, z3, x2, y2, z2);
}
w[0] = result[0];
w[1] = result[1];
w[2] = result[2];
}
// PRIVATE FUNCTIONS
static void FillTriangleFlatBottom(
uint32_t *buffer, int width,
float *zbuffer, uint32_t color,
float x0, float y0, float z0,
float x1, float y1, float z1,
float x2, float y2, float z2)
// PUBLIC FUNCTIONS
void FillTriangle(
Engine_Buffer &buffer, ColorU32 &color,
Point &v0, Point &v1, Point &v2)
{
if (x2 < x1)
{
float temp;
SWAP(x2, x1, temp);
SWAP(y2, y1, temp);
SWAP(z2, z1, temp);
}
// Top-left fill convention
float dxdy_left = (x1 - x0) / (y1 - y0);
float dxdy_right = (x2 - x0) / (y2 - y0);
int yStart = (int)ceilf(y0);
int yEnd = (int)ceilf(y2) - 1;
float xStart = x0 + dxdy_left * (yStart - y0);
float xEnd = x0 + dxdy_right * (yStart - y0);
BoundingBox box(v0, v1, v2);
int yMin = (int)ceilf(box.yMin);
int yMax = (int)ceilf(box.yMax) - 1;
int xMin = (int)ceilf(box.xMin);
int xMax = (int)ceilf(box.xMax) - 1;
// Inverse z-buffering
float z0Inv = 1.0f / z0;
float z1Inv = 1.0f / z1;
float z2Inv = 1.0f / z2;
float dzdy_left = (z1Inv - z0Inv) / (y1 - y0);
float dzdy_right = (z2Inv - z0Inv) / (y2 - y0);
float zStart = z0Inv;
float zEnd = z0Inv;
// Fill
for (int y = yStart; y <= yEnd; ++y)
for (int y = yMin; y <= yMax; ++y)
{
float dzdx = (zEnd - zStart) / (xEnd - xStart);
float z = zStart;
int xStartInt = (int)xStart;
int xEndInt = (int)xEnd;
for (int x = xStartInt; x <= xEndInt; ++x)
for (int x = xMin; x <= xMax; ++x)
{
int pixel = (y * width) + x;
if (z > zbuffer[pixel])
{
DrawPixel(buffer, width, color, x, y);
zbuffer[pixel] = z;
}
z += dzdx;
}
xStart += dxdy_left;
xEnd += dxdy_right;
zStart += dzdy_left;
zEnd += dzdy_right;
}
}
Point p(x, y, 1.0f);
static void FillTriangleFlatTop(
uint32_t *buffer, int width,
float *zbuffer, uint32_t color,
float x0, float y0, float z0,
float x1, float y1, float z1,
float x2, float y2, float z2)
{
if (x1 < x0)
{
float temp;
SWAP(x1, x0, temp);
SWAP(y1, y0, temp);
SWAP(z1, z0, temp);
}
float barycenter[3];
// Top-left fill convention
float dxdy_left = (x2 - x0) / (y2 - y0);
float dxdy_right = (x2 - x1) / (y2 - y1);
int yStart = (int)ceilf(y0);
int yEnd = (int)ceilf(y2) - 1;
float xStart = x0 + dxdy_left * (yStart - y0);
float xEnd = x1 + dxdy_right * (yStart - y0);
// Inverse z-buffering
float z0Inv = 1.0f / z0;
float z1Inv = 1.0f / z1;
float z2Inv = 1.0f / z2;
float dzdy_left = (z2Inv - z0Inv) / (y2 - y0);
float dzdy_right = (z2Inv - z1Inv) / (y2 - y1);
float zStart = z0Inv;
float zEnd = z1Inv;
// Fill
for (int y = yStart; y <= yEnd; ++y)
{
float dzdx = (zEnd - zStart) / (xEnd - xStart);
float z = zStart;
ComputeBarycenter(barycenter, v0, v1, v2, p);
int xStartInt = (int)xStart;
int xEndInt = (int)xEnd;
if (barycenter[0] >= 0 && barycenter[1] >= 0 && barycenter[2] >= 0)
{
float zInv =
(barycenter[0] * (1.0f/v0.z))
+ (barycenter[1] * (1.0f/v1.z))
+ (barycenter[2] * (1.0f/v2.z));
for (int x = xStartInt; x <= xEndInt; ++x)
{
int pixel = (y * width) + x;
int pixel = (y * buffer.width + x);
if (z > zbuffer[pixel])
{
DrawPixel(buffer, width, color, x, y);
if (zInv > buffer.zbuffer[pixel])
{
DrawPixel(buffer.buffer, buffer.width, color.u32, x, y);
zbuffer[pixel] = z;
buffer.zbuffer[pixel] = zInv;
}
}
z += dzdx;
}
xStart += dxdy_left;
xEnd += dxdy_right;
zStart += dzdy_left;
zEnd += dzdy_right;
}
}

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