Repository: glouw/gel
Branch: master
Commit: 26194d77b2f4
Files: 5
Total size: 15.8 KB

Directory structure:
gitextract_9ojlyfb4/

├── .gitignore
├── LICENSE
├── Makefile
├── README.md
└── main.c

================================================
FILE CONTENTS
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================================================
FILE: .gitignore
================================================
gel
obj/


================================================
FILE: LICENSE
================================================
MIT License

Copyright (c) 2018 Gustav Louw

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.


================================================
FILE: Makefile
================================================
BIN = gel

CFLAGS = -std=c99 -Wall -Wextra -pedantic -Ofast -flto -march=native

LDFLAGS = -lm -lSDL2 -lSDL2_image

CC = gcc

SRC = main.c

all:
	$(CC) $(CFLAGS) $(LDFLAGS) $(SRC) -o $(BIN)

run:
	./$(BIN)

clean:
	rm -f $(BIN)


================================================
FILE: README.md
================================================
![screenshot](img/logo.png)

Gel (Graphical Emulation Layer) is an N64-like software renderer.

    make; ./gel path/to/obj path/to/bmp

Dependencies:

    SDL2-devel
    SDL2-image-devel

Models, for educational purposes, can be found here:

    https://www.models-resource.com/nintendo_64/

Models must be bundled with a single obj file and texture file. The obj file
must include vertex normals.

Rotate the screen with the mouse.

![screenshot](img/salesman.gif)


================================================
FILE: main.c
================================================
#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>
#include <stdlib.h>
#include <stdio.h>
#include <float.h>
#include <math.h>

typedef struct
{
    float x, y, z;
}
Vertex;

typedef struct
{
    Vertex* vertex;
    int count;
    int max;
}
Vertices;

typedef struct
{
    int va, vb, vc;
    int ta, tb, tc;
    int na, nb, nc;
}
Face;

typedef struct
{
    Face* face;
    int count;
    int max;
}
Faces;

typedef struct
{
    Vertices vsv, vsn, vst;
    Faces fs;
}
Obj;

typedef struct
{
    Vertex a, b, c;
}
Triangle;

typedef struct
{
    Triangle* triangle;
    int count;
}
Triangles;

typedef struct
{
    Triangle vew, nrm, tex;
    SDL_Surface* fdif;
}
Target;

typedef struct
{
    SDL_Window* window;
    SDL_Renderer* renderer;
    SDL_Texture* canvas;
    int xres;
    int yres;
}
Sdl;

typedef struct
{
    float xt;
    float yt;
    float sens;
    int done;
}
Input;

static int flns(FILE* const file)
{
    int ch = EOF;
    int lines = 0;
    int pc = '\n';
    while((ch = getc(file)) != EOF)
    {
        if(ch == '\n')
            lines++;
        pc = ch;
    }
    if(pc != '\n')
        lines++;
    rewind(file);
    return lines;
}

static char* freadln(FILE* const file)
{
    int ch = EOF;
    int reads = 0;
    int size = 128;
    char* line = (char*) malloc(sizeof(char) * size);
    while((ch = getc(file)) != '\n' && ch != EOF)
    {
        line[reads++] = ch;
        if(reads + 1 == size)
            line = (char*) realloc(line, sizeof(char) * (size *= 2));
    }
    line[reads] = '\0';
    return line;
}

static Vertices vsnew(const int max)
{
    const Vertices vs = { (Vertex*) malloc(sizeof(Vertex) * max), 0, max };
    return vs;
}

static Faces fsnew(const int max)
{
    const Faces fs = { (Face*) malloc(sizeof(Face) * max), 0, max };
    return fs;
}

static Obj oparse(FILE* const file)
{
    const int lines = flns(file);
    const int size = 128;
    Vertices vsv = vsnew(size);
    Vertices vsn = vsnew(size);
    Vertices vst = vsnew(size);
    Faces fs = fsnew(size);
    for(int i = 0; i < lines; i++)
    {
        Face f;
        Vertex v;
        char* line = freadln(file);
        if(line[0] == 'v' && line[1] == 'n')
        {
            if(vsn.count == vsn.max)
                vsn.vertex = (Vertex*) realloc(vsn.vertex, sizeof(Vertex) * (vsn.max *= 2));
            sscanf(line, "vn %f %f %f", &v.x, &v.y, &v.z);
            vsn.vertex[vsn.count++] = v;
        }
        else if(line[0] == 'v' && line[1] == 't')
        {
            if(vst.count == vst.max)
                vst.vertex = (Vertex*) realloc(vst.vertex, sizeof(Vertex) * (vst.max *= 2));
            sscanf(line, "vt %f %f %f", &v.x, &v.y, &v.z);
            vst.vertex[vst.count++] = v;
        }
        else if(line[0] == 'v')
        {
            if(vsv.count == vsv.max)
                vsv.vertex = (Vertex*) realloc(vsv.vertex, sizeof(Vertex) * (vsv.max *= 2));
            sscanf(line, "v %f %f %f", &v.x, &v.y, &v.z);
            vsv.vertex[vsv.count++] = v;
        }
        else if(line[0] == 'f')
        {
            if(fs.count == fs.max)
                fs.face = (Face*) realloc(fs.face, sizeof(Face) * (fs.max *= 2));
            sscanf(line, "f %d/%d/%d %d/%d/%d %d/%d/%d", &f.va, &f.ta, &f.na, &f.vb, &f.tb, &f.nb, &f.vc, &f.tc, &f.nc);
            const Face indexed = {
                f.va - 1, f.vb - 1, f.vc - 1,
                f.ta - 1, f.tb - 1, f.tc - 1,
                f.na - 1, f.nb - 1, f.nc - 1
            };
            fs.face[fs.count++] = indexed;
        }
        free(line);
    }
    rewind(file);
    const Obj obj = { vsv, vsn, vst, fs };
    return obj;
}

static Vertex vsub(const Vertex a, const Vertex b)
{
    const Vertex v = { a.x - b.x, a.y - b.y, a.z - b.z };
    return v;
}

static Vertex vcross(const Vertex a, const Vertex b)
{
    const Vertex c = { a.y * b.z - a.z * b.y, a.z * b.x - a.x * b.z, a.x * b.y - a.y * b.x };
    return c;
}

static Vertex vmul(const Vertex v, const float n)
{
    const Vertex m = { v.x * n, v.y * n, v.z * n };
    return m;
}

static float vdot(const Vertex a, const Vertex b)
{
    return a.x * b.x + a.y * b.y + a.z * b.z;
}

static float vlen(const Vertex v)
{
    return sqrtf(v.x * v.x + v.y * v.y + v.z * v.z);
}

static Vertex vunit(const Vertex v)
{
    return vmul(v, 1.0f / vlen(v));
}

static Triangle tunit(const Triangle t)
{
    const Triangle u = { vunit(t.a), vunit(t.b), vunit(t.c) };
    return u;
}

static Triangle tmul(const Triangle t, const float scale)
{
    const Triangle s = { vmul(t.a, scale), vmul(t.b, scale), vmul(t.c, scale) };
    return s;
}

static Triangles tsnew(const int count)
{
    const Triangles ts = { (Triangle*) malloc(sizeof(Triangle) * count), count };
    return ts;
}

static float vmaxlen(const Vertices vsv)
{
    float max = 0.0f;
    for(int i = 0; i < vsv.count; i++)
        if(vlen(vsv.vertex[i]) > max)
            max = vlen(vsv.vertex[i]);
    return max;
}

static Triangles tvgen(const Obj obj)
{
    const int scale = vmaxlen(obj.vsv);
    Triangles tv = tsnew(obj.fs.count);
    for(int i = 0; i < obj.fs.count; i++)
    {
        const Triangle t = {
            obj.vsv.vertex[obj.fs.face[i].va],
            obj.vsv.vertex[obj.fs.face[i].vb],
            obj.vsv.vertex[obj.fs.face[i].vc],
        };
        tv.triangle[i] = tmul(t, 1.0f / scale);
    }
    return tv;
}

static Triangles tngen(const Obj obj)
{
    Triangles tn = tsnew(obj.fs.count);
    for(int i = 0; i < obj.fs.count; i++)
    {
        const Triangle t = {
            obj.vsn.vertex[obj.fs.face[i].na],
            obj.vsn.vertex[obj.fs.face[i].nb],
            obj.vsn.vertex[obj.fs.face[i].nc],
        };
        tn.triangle[i] = t;
    }
    return tn;
}

static Triangles ttgen(const Obj obj)
{
    Triangles tt = tsnew(obj.fs.count);
    for(int i = 0; i < obj.fs.count; i++)
    {
        const Triangle t = {
            obj.vst.vertex[obj.fs.face[i].ta],
            obj.vst.vertex[obj.fs.face[i].tb],
            obj.vst.vertex[obj.fs.face[i].tc],
        };
        tt.triangle[i] = t;
    }
    return tt;
}

static Triangle tviewport(const Triangle t, const Sdl sdl)
{
    const float w = sdl.yres / 1.5f;
    const float h = sdl.yres / 1.5f;
    const float x = sdl.xres / 2.0f;
    const float y = sdl.yres / 4.0f;
    const Triangle v = {
        { w * t.a.x + x, h * t.a.y + y, (t.a.z + 1.0f) / 1.5f },
        { w * t.b.x + x, h * t.b.y + y, (t.b.z + 1.0f) / 1.5f },
        { w * t.c.x + x, h * t.c.y + y, (t.c.z + 1.0f) / 1.5f },
    };
    return v;
}

static Triangle tperspective(const Triangle t)
{
    const float c = 3.0f;
    const float za = 1.0f - t.a.z / c;
    const float zb = 1.0f - t.b.z / c;
    const float zc = 1.0f - t.c.z / c;
    const Triangle p = {
        { t.a.x / za, t.a.y / za, t.a.z / za },
        { t.b.x / zb, t.b.y / zb, t.b.z / zb },
        { t.c.x / zc, t.c.y / zc, t.c.z / zc },
    };
    return p;
}

static Vertex tbarycenter(const Triangle t, const int x, const int y)
{
    const Vertex p = { (float) x, (float) y, 0.0f };
    const Vertex v0 = vsub(t.b, t.a);
    const Vertex v1 = vsub(t.c, t.a);
    const Vertex v2 = vsub(p, t.a);
    const float d00 = vdot(v0, v0);
    const float d01 = vdot(v0, v1);
    const float d11 = vdot(v1, v1);
    const float d20 = vdot(v2, v0);
    const float d21 = vdot(v2, v1);
    const float v = (d11 * d20 - d01 * d21) / (d00 * d11 - d01 * d01);
    const float w = (d00 * d21 - d01 * d20) / (d00 * d11 - d01 * d01);
    const float u = 1.0f - v - w;
    const Vertex vertex = { v, w, u };
    return vertex;
}

static uint32_t pshade(const uint32_t pixel, const int shading)
{
    const uint32_t r = (((pixel >> 0x10) /****/) * shading) >> 0x08;
    const uint32_t g = (((pixel >> 0x08) & 0xFF) * shading) >> 0x08;
    const uint32_t b = (((pixel /*****/) & 0xFF) * shading) >> 0x08;
    return r << 0x10 | g << 0x08 | b;
}

static void tdraw(const int yres, uint32_t* const pixel, float* const zbuff, const Target t, const Vertex lights)
{
    const int x0 = fminf(t.vew.a.x, fminf(t.vew.b.x, t.vew.c.x));
    const int y0 = fminf(t.vew.a.y, fminf(t.vew.b.y, t.vew.c.y));
    const int x1 = fmaxf(t.vew.a.x, fmaxf(t.vew.b.x, t.vew.c.x));
    const int y1 = fmaxf(t.vew.a.y, fmaxf(t.vew.b.y, t.vew.c.y));
    for(int x = x0; x <= x1; x++)
    for(int y = y0; y <= y1; y++)
    {
        const Vertex bc = tbarycenter(t.vew, x, y);
        if(bc.x >= 0.0f && bc.y >= 0.0f && bc.z >= 0.0f)
        {
            // Barycenter above is upwards. Everything below rotated 90 degrees to accomodate sideways renderer.
            const float z = bc.x * t.vew.b.z + bc.y * t.vew.c.z + bc.z * t.vew.a.z;
            if(z > zbuff[y + x * yres])
            {
                const Vertex varying = { vdot(lights, t.nrm.b), vdot(lights, t.nrm.c), vdot(lights, t.nrm.a) };
                const uint32_t* const pixels = (uint32_t*) t.fdif->pixels;
                const int xx = (t.fdif->w - 1) * (0.0f + (bc.x * t.tex.b.x + bc.y * t.tex.c.x + bc.z * t.tex.a.x));
                const int yy = (t.fdif->h - 1) * (1.0f - (bc.x * t.tex.b.y + bc.y * t.tex.c.y + bc.z * t.tex.a.y));
                const float intensity = vdot(bc, varying);
                const int shading = 0xFF * (intensity < 0.0f ? 0.0f : intensity > 1.0f ? 1.0f : intensity);
                // Image is upwards contrary to sideways renderer.
                zbuff[y + x * yres] = z;
                pixel[y + x * yres] = pshade(pixels[xx + yy * t.fdif->w], shading);
            }
        }
    }
}

static Triangle tviewtri(const Triangle t, const Vertex x, const Vertex y, const Vertex z, const Vertex eye)
{
    const Triangle o = {
        { vdot(t.a, x) - vdot(x, eye), vdot(t.a, y) - vdot(y, eye), vdot(t.a, z) - vdot(z, eye) },
        { vdot(t.b, x) - vdot(x, eye), vdot(t.b, y) - vdot(y, eye), vdot(t.b, z) - vdot(z, eye) },
        { vdot(t.c, x) - vdot(x, eye), vdot(t.c, y) - vdot(y, eye), vdot(t.c, z) - vdot(z, eye) },
    };
    return o;
}

static Triangle tviewnrm(const Triangle n, const Vertex x, const Vertex y, const Vertex z)
{
    const Triangle o = {
        { vdot(n.a, x), vdot(n.a, y), vdot(n.a, z) },
        { vdot(n.b, x), vdot(n.b, y), vdot(n.b, z) },
        { vdot(n.c, x), vdot(n.c, y), vdot(n.c, z) },
    };
    return tunit(o);
}

static Input iinit()
{
    const Input input = { 0.0f, 0.0f, 0.005f, 0 };
    SDL_SetRelativeMouseMode(SDL_FALSE);
    return input;
}

static Input ipump(Input input)
{
    int dx;
    int dy;
    SDL_Event event;
    SDL_PollEvent(&event);
    if(event.type == SDL_QUIT)
        input.done = 1;
    SDL_GetRelativeMouseState(&dx, &dy);
    input.xt -= input.sens * dx;
    input.yt += input.sens * dy;
    return input;
}

static void reset(float* const zbuff, uint32_t* const pixel, const int size)
{
    for(int i = 0; i < size; i++)
        zbuff[i] = -FLT_MAX, pixel[i] = 0x0;
}

static void spresent(const Sdl sdl)
{
    SDL_RenderPresent(sdl.renderer);
}

static void schurn(const Sdl sdl)
{
    const SDL_Rect dst = {
        (sdl.xres - sdl.yres) / 2,
        (sdl.yres - sdl.xres) / 2,
        sdl.yres, sdl.xres
    };
    SDL_RenderCopyEx(sdl.renderer, sdl.canvas, NULL, &dst, -90, NULL, SDL_FLIP_NONE);
}

static Sdl ssetup(const int xres, const int yres)
{
    Sdl sdl;
    SDL_Init(SDL_INIT_VIDEO);
    SDL_CreateWindowAndRenderer(xres, yres, 0, &sdl.window, &sdl.renderer);
    SDL_SetWindowTitle(sdl.window, "Gel-1.2");
    // Notice the flip between xres and yres - the renderer is on its side to maximize cache effeciency.
    sdl.canvas = SDL_CreateTexture(sdl.renderer, SDL_PIXELFORMAT_ARGB8888, SDL_TEXTUREACCESS_STREAMING, yres, xres);
    sdl.xres = xres;
    sdl.yres = yres;
    return sdl;
}

static void sunlock(const Sdl sdl)
{
    SDL_UnlockTexture(sdl.canvas);
}

static uint32_t* slock(const Sdl sdl)
{
    void* pixel;
    int pitch;
    SDL_LockTexture(sdl.canvas, NULL, &pixel, &pitch);
    return (uint32_t*) pixel;
}

static FILE* oload(const char* const path)
{
    FILE* const file = fopen(path, "r");
    if(file == NULL)
    {
        printf("could not open %s\n", path);
        exit(1);
    }
    return file;
}

static SDL_Surface* sload(const char* const path)
{
    SDL_Surface* const bmp = IMG_Load(path);
    if(bmp == NULL)
    {
        puts(IMG_GetError());
        exit(1);
    }
    SDL_PixelFormat* const allocation = SDL_AllocFormat(SDL_PIXELFORMAT_RGB888);
    SDL_Surface* const converted = SDL_ConvertSurface(bmp, allocation, 0);
    SDL_FreeFormat(allocation);
    SDL_FreeSurface(bmp);
    return converted;
}

int main(int argc, char* argv[])
{
    if(argc != 3)
    {
        puts("args: path/to/obj path/to/bmp");
        return 1;
    }
    FILE* const fobj = oload(argv[1]);
    SDL_Surface* const fdif = sload(argv[2]);
    const Obj obj = oparse(fobj);
    const Triangles tv = tvgen(obj); // Triangle Vertices.
    const Triangles tt = ttgen(obj); // Triangle Textures.
    const Triangles tn = tngen(obj); // Triangle Normals.
    const Sdl sdl = ssetup(800, 600);
    float* const zbuff = (float*) malloc(sizeof(float) * sdl.xres * sdl.yres);
    for(Input input = iinit(); !input.done; input = ipump(input))
    {
        const int t0 = SDL_GetTicks();
        uint32_t* const pixel = slock(sdl);
        reset(zbuff, pixel, sdl.xres * sdl.yres);
        const Vertex center = { 0.0f, 0.0f, 0.0f };
        const Vertex upward = { 0.0f, 1.0f, 0.0f };
        const Vertex lights = { 0.0f, 0.0f, 1.0f };
        const Vertex eye = { sinf(input.xt), sinf(input.yt), cosf(input.xt) };
        const Vertex z = vunit(vsub(eye, center));
        const Vertex x = vunit(vcross(upward, z));
        const Vertex y = vcross(z, x);
        for(int i = 0; i < tv.count; i++)
        {
            const Triangle nrm = tviewnrm(tn.triangle[i], x, y, z);
            const Triangle tex = tt.triangle[i];
            const Triangle tri = tviewtri(tv.triangle[i], x, y, z, eye);
            const Triangle per = tperspective(tri);
            const Triangle vew = tviewport(per, sdl);
            const Target target = { vew, nrm, tex, fdif };
            tdraw(sdl.yres, pixel, zbuff, target, lights);
        }
        sunlock(sdl);
        schurn(sdl);
        spresent(sdl);
        const int t1 = SDL_GetTicks();
        const int ms = 1000.0f / 60.0f - (t1 - t0);
        SDL_Delay(ms < 0 ? 0 : ms);
    }
    return 0;
}