Handmade Hero » Forums » Code » Trouble with software 3d renderer
Croepha
David Butler
68 posts
1 project

I love pretty much anything technical, whether it be programming, networking, hacking or electronics.

#7636 Trouble with software 3d renderer
1 year, 5 months ago


Over the weekend I thought it might be fun to implement a very basic 3d wireframe renderer. I basically copied all the math from the OpenGL docs and used sgorsten's vector math library.

This is what I got so far:

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/*

watch -n.1 "clang++ --std=c++11 -g main.cpp -shared -o _target.so && mv _target.so target.so"


# clang++ --std=c++11 -g main.cpp  -o target && ./target
*/
#include <assert.h>
#include <stdio.h>
#include "linalg.h"
#include <math.h>
#include <time.h>

#define FOR_RANGE(index, count) for ((index) = 0; (index) < (count); (index)++)

using namespace linalg::aliases;
using namespace linalg;

struct GC {
    unsigned char * render_buffer;
    int width;
    int height;
    float near;
    float far;
};

void draw_line(float2 p1, float2 p2, GC *gc) {

    if (p1[0] == INFINITY || p1[0] == -INFINITY || isnan(p1[0]) ||
        p1[1] == INFINITY || p1[1] == -INFINITY || isnan(p1[1]) ||
        p2[0] == INFINITY || p2[0] == -INFINITY || isnan(p2[0]) ||
        p2[1] == INFINITY || p2[1] == -INFINITY || isnan(p2[1])) return;

    float2 d = normalize(p2 - p1);
    float2 last_p = p1;

    float minx = p1[0];
    if (p2[0] < p1[0]) minx = p2[0];
    float miny = p1[1];
    if (p2[1] < p1[1]) miny = p2[1];
    float maxx = p1[0];
    if (p2[0] > p1[0]) maxx = p2[0];
    float maxy = p1[1];
    if (p2[1] > p1[1]) maxy = p2[1];

    for(;;) {

        int x = last_p[0];
        int y = last_p[1];
        if (x >= 0 && y>=0 && x <gc->width && y < gc->height) {
            *(gc->render_buffer + 4 * (x + gc->width * y) + 0) = 0x00;
            *(gc->render_buffer + 4 * (x + gc->width * y) + 1) = 0x00;
            *(gc->render_buffer + 4 * (x + gc->width * y) + 2) = 0x00;
            *(gc->render_buffer + 4 * (x + gc->width * y) + 3) = 0xFF;
        }
        // else { printf("clip!\n");};

        last_p += d;
        if ( (d[0]==0 && d[1]==0) ||
            d[0] == INFINITY || d[0] == -INFINITY || isnan(d[0]) ||
            d[1] == INFINITY || d[1] == -INFINITY || isnan(d[1]) ||
            last_p[0] < minx ||
            last_p[1] < miny ||
            last_p[0] > maxx ||
            last_p[1] > maxy
        ) break;
    }

}


float4x4 look_at() {
     // gluLookAt
     float la_ey_x = 0.0f;
     float la_ey_y = 0.0f;
     float la_ey_z = 5.0f;
     float la_cn_x = 0.0f;
     float la_cn_y = 0.0f;
     float la_cn_z = 0.0f;
     float la_up_x = 0.0f;
     float la_up_y = 1.0f;
     float la_up_z = 0.0f;

     float3 la_F = {la_cn_x - la_ey_x, la_cn_y - la_ey_y, la_cn_z - la_ey_z};
     float3 la_UP = {la_up_x, la_up_y, la_up_z};

     float3 la_f = normalize(la_F);
     float3 la_UP_norm = normalize(la_UP);


//     float3 la_s = la_f * la_UP_norm;
//     float3 la_u = normalize(la_s) * la_f;
     float3 la_s = cross(la_f, la_UP_norm);
     float3 la_u = cross(normalize(la_s), la_f);


    return                {{  la_s[0],  la_s[1],  la_s[2],  0},
                           {  la_u[0],  la_u[1],  la_u[2],  0},
                           { -la_f[0], -la_f[1], -la_f[2],  0},
                           {        0,        0,        0,  1}};

}


float4x4 translate(float3 trans_p) {
    return              {{  1,  0,  0,  trans_p[0]},
                         {  0,  1,  0,  trans_p[1]},
                         {  0,  0,  1,  trans_p[2]},
                         {  0,  0,  0,  1}};
}

float4x4 rotate(float3 r_p, float r_angle) {
    r_p = normalize(r_p);
    float r_c = cos(r_angle * M_PI / 180);
    float r_s = sin(r_angle * M_PI / 180);

    return {{ powf(r_p.x, 2) * (1 - r_c) + r_c,            r_p.x * r_p.y * (1 - r_c) - r_p.z * r_s,      r_p.x * r_p.z * (1-r_c) + r_p.y * r_s,   0 },
            { r_p.y * r_p.x * (1 - r_c) +  r_p.z * r_s,   powf(r_p.y, 2) * (1 - r_c) + r_c,              r_p.y * r_p.z * (1-r_c) - r_p.x * r_s,   0 },
            { r_p.x * r_p.z * (1 - r_c) -  r_p.y * r_s,   r_p.y * r_p.z * (1 - r_c) +  r_p.x * r_s,     powf(r_p.z, 2) * (1 - r_c) + r_c,         0 },
            { 0,                                          0,                                            0,                                       1 }};

}

float4x4 ortho() {
    float o_left      = -2.0f;
    float o_right     =  2.0f;
    float o_bottom    = -2.0f;
    float o_top       =  2.0f;
    float o_near      = -2.0f;
    float o_far       =  2.0f;

    float o_tx = (o_right + o_left) / (o_right - o_left);
    float o_ty = (o_top + o_bottom) / (o_top - o_bottom);
    float o_tz = (o_far + o_near) / (o_far - o_near);

    return     {{ 2.0f / (o_right - o_left), 0, 0, o_tx},
                { 0,                         2.0f / (o_top - o_bottom), 0, o_ty},
                { 0,              0, 2.0f / (o_far - o_near), o_tz},
                { 0,              0, -1, 1}};

}

float4x4 perspective() {

    // gluPerspective
    float field_of_view = 40.0f;
    float aspect_ratio = 1.0f;
    float z_near = 8.60f;
    float z_far = 10.0f;

    // float f = cotangent(field_of_view / 2.0f);
    float f = 1.0f / tan(field_of_view / (float)(M_PI) / 180.0f / 2.0f);

    float4x4 projection = {{ f/aspect_ratio,  0, 0, 0},
                            { 0,              f, 0, 0},
                            { 0,              0, (z_far + z_near) / (z_near - z_far), (2.0f * z_far * z_near) / (z_near - z_far)},
                            { 0,              0, -1, 0}};

    return  {{ f/aspect_ratio,  1, 0, 0},
             { 0,              f, 0, 0},
             { 0,              0, (z_far + z_near) / (z_near - z_far), (2.0f * z_far * z_near) / (z_near - z_far)},
             { 0,              0, -1, 0}};

}


float3 nd_cord(GC* gc, float4 clip_cord) {
    return { clip_cord.x / clip_cord.w, clip_cord.y / clip_cord.w, clip_cord.z / clip_cord.w};
}

float3 window_cord(GC* gc, float3 nd_cord) {
    float vp_x       = 0;                   // glViewport
    float vp_y       = 0;                   // glViewport
    float vp_w       = gc->width;      // glViewport
    float vp_h       = gc->height;     // glViewport
    float dr_n       = gc->near;    //glDepthRange
    float dr_f       = gc->far;     //glDepthRange

    return {
        (vp_w / 2.0f) * nd_cord.x + (vp_x + vp_w/2.0f),
        (vp_h / 2.0f) * nd_cord.y + (vp_y + vp_h/2.0f),
        ((dr_f - dr_n)/2.0f) * nd_cord.z + (dr_f + dr_n)/2.0f
    };

}



extern "C" void target(float current_time, void * _render_buffer, int width, int height) {

    GC  gc = {(unsigned char *)_render_buffer, width, height, 1, 10};

    unsigned char * render_buffer = (unsigned char *)_render_buffer;

//    printf("\033[1A");
//    printf("\033[1A");
//    printf("\033[1A");
//    printf("\033[1A");
//    printf("\033[1A");
//    printf("\033[1A");


    // Clear white
    memset(render_buffer, 0xFF, width * height * 4);

    float4x4 identity = {{  1,  0,  0 , 0},
                         {  0,  1,  0,  0},
                         {  0,  0,  1,  0},
                         {  0,  0,  0,  1}};

    // Object cords
    float4 oc_p0 = { 1,  1,  1, 1};
    float4 oc_p1 = { 1,  1, -1, 1};
    float4 oc_p2 = { 1, -1, -1, 1};
    float4 oc_p3 = { 1, -1,  1, 1};
    float4 oc_p4 = {-1,  1,  1, 1};
    float4 oc_p5 = {-1,  1, -1, 1};
    float4 oc_p6 = {-1, -1, -1, 1};
    float4 oc_p7 = {-1, -1,  1, 1};
    // Cube with lines: p0, p1,   p1,p2    p2,p3   p3,p0      p4,p5   p5,p6   p6,p7   p7,p4    p0,p4   p1,p5   p2,p6   p3,p7


    float4x4 model_view = identity;

    // model_view = mul(model_view, look_at());

    // model_view = mul(model_view, translate({0.0, 0.0, -1.0}));

    model_view = mul(model_view, rotate({1.0, 0.0, 0.0},  20.0f));
    model_view = mul(model_view, rotate({0.0, 0.0, 1.0}, -10.0f));
    model_view = mul(model_view, rotate({0.0, 1.0, 0.0}, -10.0f));


    // eye cords
    float4 ec_p0 = mul(model_view, oc_p0);
    float4 ec_p1 = mul(model_view, oc_p1);
    float4 ec_p2 = mul(model_view, oc_p2);
    float4 ec_p3 = mul(model_view, oc_p3);
    float4 ec_p4 = mul(model_view, oc_p4);
    float4 ec_p5 = mul(model_view, oc_p5);
    float4 ec_p6 = mul(model_view, oc_p6);
    float4 ec_p7 = mul(model_view, oc_p7);




    float4x4 projection = identity;
    projection = mul(projection, ortho());
    //projection = mul(projection, perspective());



    // clip cords
    float4 cc_p0 = mul(projection, ec_p0);
    float4 cc_p1 = mul(projection, ec_p1);
    float4 cc_p2 = mul(projection, ec_p2);
    float4 cc_p3 = mul(projection, ec_p3);
    float4 cc_p4 = mul(projection, ec_p4);
    float4 cc_p5 = mul(projection, ec_p5);
    float4 cc_p6 = mul(projection, ec_p6);
    float4 cc_p7 = mul(projection, ec_p7);

    // Normalized device coordinates
    float3 ndc_p0 = nd_cord(&gc, cc_p0);
    float3 ndc_p1 = nd_cord(&gc, cc_p1);
    float3 ndc_p2 = nd_cord(&gc, cc_p2);
    float3 ndc_p3 = nd_cord(&gc, cc_p3);
    float3 ndc_p4 = nd_cord(&gc, cc_p4);
    float3 ndc_p5 = nd_cord(&gc, cc_p5);
    float3 ndc_p6 = nd_cord(&gc, cc_p6);
    float3 ndc_p7 = nd_cord(&gc, cc_p7);

    // Window Cords
    float3 wc_p0 = window_cord(&gc, ndc_p0);
    float3 wc_p1 = window_cord(&gc, ndc_p1);
    float3 wc_p2 = window_cord(&gc, ndc_p2);
    float3 wc_p3 = window_cord(&gc, ndc_p3);
    float3 wc_p4 = window_cord(&gc, ndc_p4);
    float3 wc_p5 = window_cord(&gc, ndc_p5);
    float3 wc_p6 = window_cord(&gc, ndc_p6);
    float3 wc_p7 = window_cord(&gc, ndc_p7);


#if 0

    time_t timer;
    char buffer[26];
    struct tm* tm_info;

    time(&timer);
    tm_info = localtime(&timer);

    strftime(buffer, 26, "%Y:%m:%d %H:%M:%S", tm_info);

    printf("%s  Points 0:%f,%f 1:%f,%f 2:%f,%f 3:%f,%f 4:%f,%f 5:%f,%f 6:%f,%f 7:%f,%f \n",
        buffer,
        wc_p0[0], wc_p0[1], wc_p1[0], wc_p1[1], wc_p2[0], wc_p2[1], wc_p3[0], wc_p3[1],
        wc_p4[0], wc_p4[1], wc_p5[0], wc_p5[1], wc_p6[0], wc_p6[1], wc_p7[0], wc_p7[1]
    );
    printf("%s  Pointz 0:%f    1:%f    2:%f    3:%f    4:%f    5:%f    6:%f    7:%f  \n",
        buffer,
        wc_p0[2], wc_p1[2], wc_p2[2], wc_p3[2], wc_p4[2], wc_p5[2], wc_p6[2], wc_p7[2]
    );
#endif
    // lines: p0, p1,   p1,p2    p2,p3   p3,p0      p4,p5   p5,p6   p6,p7   p7,p4    p0,p4   p1,p5   p2,p6   p3,p7

    draw_line({wc_p0[0], wc_p0[1]}, {wc_p1[0], wc_p1[1]}, &gc);
    draw_line({wc_p1[0], wc_p1[1]}, {wc_p2[0], wc_p2[1]}, &gc);
    draw_line({wc_p2[0], wc_p2[1]}, {wc_p3[0], wc_p3[1]}, &gc);
    draw_line({wc_p3[0], wc_p3[1]}, {wc_p0[0], wc_p0[1]}, &gc);
    draw_line({wc_p4[0], wc_p4[1]}, {wc_p5[0], wc_p5[1]}, &gc);
    draw_line({wc_p5[0], wc_p5[1]}, {wc_p6[0], wc_p6[1]}, &gc);
    draw_line({wc_p6[0], wc_p6[1]}, {wc_p7[0], wc_p7[1]}, &gc);
    draw_line({wc_p7[0], wc_p7[1]}, {wc_p4[0], wc_p4[1]}, &gc);
    draw_line({wc_p0[0], wc_p0[1]}, {wc_p4[0], wc_p4[1]}, &gc);
    draw_line({wc_p1[0], wc_p1[1]}, {wc_p5[0], wc_p5[1]}, &gc);
    draw_line({wc_p2[0], wc_p2[1]}, {wc_p6[0], wc_p6[1]}, &gc);
    draw_line({wc_p3[0], wc_p3[1]}, {wc_p7[0], wc_p7[1]}, &gc);


}


See also: Gist, along with hot-loader (For OS X, but should run on anywhere, along as you have SDL)

If I just use orthographic projection I get something that I expect:


However, if I get try to use a perspective matrix, or even apply a translation matrix, I get really odd results:



I'm kinda at a loss at this point, I checked the math a few times, but I probably still have a mistake somewhere...

Anyway, here is what I based the code off of:
"OpenGL Transformation" Basicall...ertices translate to window cords
glTranslate
gluPerspective


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Croepha
David Butler
68 posts
1 project

I love pretty much anything technical, whether it be programming, networking, hacking or electronics.

#7648 Trouble with software 3d renderer
1 year, 5 months ago

Ugg, I feel like such an idiot... "linalg.h" wants everything in column major order, so all my matrices were inverted...

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