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#include "rasterizer.h"
#include "device.h"
#include "shader.h"
#include "../math/math.h"
#include "../util/assert.h"
void ssrR_putline(int x0, int y0, int x1, int y1, Color color) {
int steep = 0;
if (abs(x0 - x1) < abs(y0 - y1)) {
swapi(x0, y0);
swapi(x1, y1);
steep = 1;
}
if (x0 > x1) {
swapi(x0, x1);
swapi(y0, y1);
}
int dx = x1 - x0;
int dy = y1 - y0;
int derror2 = abs(dy) << 1;
int error2 = 0;
int y = y0;
for (int x = x0; x <= x1; ++x) {
if (steep) {
ssr_putpoint(y, x, color);
}
else {
ssr_putpoint(x, y, color);
}
error2 += derror2;
if (error2 > dx) {
y += (y1 > y0 ? 1 : -1);
error2 -= (dx << 1);
}
}
}
/*使用辅助梯形计算三角形面积，《3D数学基础》P245*/
float ssrR_area(Vec2* v1, Vec2* v2, Vec2* v3) {
ssr_assert(v1 && v2 && v3);
float area = 0.5f * ((v1->y - v2->y) * (v3->x - v2->x) + (v3->y - v2->y) * (v2->x - v1->x));
return area;
}
/*from https://github.com/ssloy/tinyrenderer*/
static Vec3 s[2], u;
bool ssrR_barycentric(Vec2* A, Vec2* B, Vec2* C, Vec2* p, Vec3* out) {
ssr_assert(A && B && C && p && out);
s[0].x = C->x - A->x; s[0].y = B->x - A->x; s[0].z = A->x - p->x;
s[1].x = C->y - A->y; s[1].y = B->y - A->y; s[1].z = A->y - p->y;
vec3_cross(&s[0], &s[1], &u);
if (compare(u.z, 0)) {
return 0;
} else {
float uz = 1.f / u.z;
out->x = 1 - (u.x + u.y) * uz;
out->y = u.y * uz;
out->z = u.x * uz;
return 1;
}
}
bool ssrR_ispointintriangle(Vec2* A, Vec2* B, Vec2* C, Vec2* p) {
ssr_assert(A && B && C && p);
Vec3 c; ssrR_barycentric(A, B, C, p, &c);
return c.x >= 0 && c.y >= 0 && c.z >= 0;
}
void ssrR_center(Vec2* A, Vec2* B, Vec2* C, Vec2* out) {
ssr_assert(A && B && C && out);
float k = 1 / 3.f;
out->x = k * (A->x + B->x + C->x);
out->y = k * (A->y + B->y + C->y);
}
/*
** clipc 按列排放的三角形三个顶点的齐次裁剪坐标
** program shader程序
*/
static Vec3 SA, SB, SC; // screen coords
static Vec3 bcp; // 重心坐标
void _ssrR_triangle(Vec4* CA, Vec4* CB, Vec4* CC, Vert* A, Vert* B, Vert* C, Program* program, UniformCollection* uniforms) {
ssr_assert(CA && CB && CC && program);
vec4_dividew(CA, &SA); ssrU_viewport(&SA, &SA);
vec4_dividew(CB, &SB); ssrU_viewport(&SB, &SB);
vec4_dividew(CC, &SC); ssrU_viewport(&SC, &SC);
/*根据屏幕空间的y值排序, A的y最小，B居中，C最大*/
Vec3 *sa = &SA, *sb = &SB, *sc = &SC, *tmp; Vec4* v4tmp; Vert* vtemp;
if (sb->y < sa->y) { sa = &SB; sb = &SA; v4tmp = CA; CA = CB; CB = v4tmp; vtemp = A; A = B; B = vtemp; }
if (sc->y < sb->y) { tmp = sc; sc = sb; sb = tmp; v4tmp = CC; CC = CB; CB = v4tmp; vtemp = B; B = C; C = vtemp; }
if (sc->y < sa->y) { tmp = sc; sc = sa; sa = tmp; v4tmp = CC; CC = CA; CA = v4tmp; vtemp = C; C = A; A = vtemp; }
float invkAC = (SC.x - SA.x) / (SC.y - SA.y + EPSILON);
float invkAB = (SB.x - SA.x) / (SB.y - SA.y + EPSILON);
float invkBC = (SC.x - SB.x) / (SC.y - SB.y + EPSILON);
int order = 1; if (((sb->y - sa->y) / (sb->x - sa->x) - invkAC) * invkAC > 0) { order = -1; }
FragmentShaderIn in = {A, B, C, 0};
Color color;
Vec2 l, r, p;
float depth; Vec3 cdepth = {SA.z, SB.z, SC.z};
float CAw = 1.f / CA->w, CBw = 1.f / CB->w, CCw = 1.f / CC->w;
for (p.y = sa->y; p.y <= sc->y; ++p.y) {
l.y = p.y;
r.y = p.y;
if (compare(SC.y, SA.y)) r.x = sc->x;
else r.x = sa->x + invkAC * (p.y - sa->y); /*AC*/
if (p.y <= sb->y) {
if (compare(SB.y, SA.y)) l.x = sb->x;
else l.x = sa->x + invkAB * (p.y - sa->y);
} else {
if (compare(SC.y, SB.y)) l.x = sc->x;
else l.x = sb->x + invkBC * (p.y - sb->y);
}
for (p.x = l.x; order * (r.x - p.x) >= 0; p.x += order) {
/*计算线性的（齐次裁剪空间）的重心坐标，分三步*/
if (!ssrR_barycentric(sa, sb, sc, &p, &bcp)) {
continue; /*discard fragment*/
}
bcp.x *= CAw; bcp.y *= CBw; bcp.z *= CCw;
vec3_scale(&bcp, 1.f / (bcp.x + bcp.y + bcp.z), &bcp);
/*depth test*/
depth = vec3_dot(&bcp, &cdepth) * 0.5f + 0.5f;
if (!ssr_testdepthf(p.x, p.y, depth)) {
continue; /*discard fragment*/
}
/*enter fragment shader*/
in.bc = &bcp;
program->fragmentshader(uniforms, &in, &color);
ssr_putpoint(p.x, p.y, color);
}
}
}
static Vec2 bboxmin, bboxmax;
void ssrR_triangle(Vec4* CA, Vec4* CB, Vec4* CC, Vert* A, Vert* B, Vert* C, Program* program, UniformCollection* uniforms) {
ssr_assert(CA && CB && CC && program);
vec4_dividew(CA, &SA); ssrU_viewport(&SA, &SA);
vec4_dividew(CB, &SB); ssrU_viewport(&SB, &SB);
vec4_dividew(CC, &SC); ssrU_viewport(&SC, &SC);
bboxmin.x = min(SA.x, min(SB.x, SC.x));
bboxmax.x = max(SA.x, max(SB.x, SC.x));
bboxmin.y = min(SA.y, min(SB.y, SC.y));
bboxmax.y = max(SA.y, max(SB.y, SC.y));
float CAw = 1.f / CA->w, CBw = 1.f / CB->w, CCw = 1.f / CC->w;
float depth; Vec3 cdepth = { SA.z, SB.z, SC.z };
FragmentShaderIn in = { A, B, C, 0 };
Vec2 p; Color color;
for (p.y = bboxmin.y; p.y <= bboxmax.y; ++p.y) {
for (p.x = bboxmin.x; p.x <= bboxmax.x; ++p.x) {
/*计算线性的（齐次裁剪空间）的重心坐标，分三步*/
if (!ssrR_barycentric(&SA, &SB, &SC, &p, &bcp)) {
continue; /*discard fragment*/
}
if (bcp.x < 0 || bcp.y < 0 || bcp.z < 0) {
continue; /*discard fragment*/
}
bcp.x *= CAw; bcp.y *= CBw; bcp.z *= CCw;
vec3_scale(&bcp, 1.f / (bcp.x + bcp.y + bcp.z), &bcp);
/*深度测试*/
if (ssr_isenable(ENABLEMASK_DEPTHTEST)) {
depth = vec3_dot(&bcp, &cdepth) * 0.5f + 0.5f;
if (!ssr_testdepthf(p.x, p.y, depth)) {
continue; /*discard fragment*/
}
}
/*enter fragment shader*/
in.bc = &bcp;
bool discad = program->fragmentshader(uniforms, &in, &color);
if (!discad)
ssr_putpoint(p.x, p.y, color);
}
}
//ssrR_putline(SA.x, SA.y, SB.x, SB.y, 0xffff0000);
//ssrR_putline(SA.x, SA.y, SC.x, SC.y, 0xffff0000);
//ssrR_putline(SC.x, SC.y, SB.x, SB.y, 0xffff0000);
}
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