defocus-modules/lib/raytracing.c

#include <defocus/camera.h>
#include <defocus/intrinsic_helper.h>

#include <immintrin.h>

#include <stdio.h>

DF_API void df_evaluate_ray_packet(const df_ray_packet *rays, df_image *output)
{
    const __m128 *base_x = (const __m128 *)rays->base_x; 
    const __m128 *base_y = (const __m128 *)rays->base_y;
    const __m128 *base_z = (const __m128 *)rays->base_z;
    
    const __m128 *dir_x = (const __m128 *)rays->dir_x;
    const __m128 *dir_y = (const __m128 *)rays->dir_y;
    const __m128 *dir_z = (const __m128 *)rays->dir_z;

    /* Simple test: Let rays intersect with plane at z = 350.0 */

    float PLANE_Z = 350.0f;

    __m128 plane_z = _mm_set1_ps(PLANE_Z);

    size_t ray_count = rays->ray_count;

    /* TODO(kevin): divide to multiple threads */
    for (size_t i = 0; i < ray_count; i += 4) {
        size_t index = i / 4;

        __m128 rays_base_x = base_x[index];
        __m128 rays_base_y = base_y[index];
        __m128 rays_base_z = base_z[index];
        __m128 rays_dir_x = dir_x[index];
        __m128 rays_dir_y = dir_y[index];
        __m128 rays_dir_z = dir_z[index];

        /* Solve for t: base.z + t * dir.z = plane_z 
         *              t = (plane_z - base.z) / dir.z 
         */
        __m128 delta = _mm_sub_ps(plane_z, rays_base_z);
        __m128 t = _mm_div_ps(delta, rays_dir_z);

        /* Sample p = base.z + t * dir */
        __m128 sample_p_x = _mm_mul_ps(t, rays_dir_x);
        __m128 sample_p_y = _mm_mul_ps(t, rays_dir_y);
        __m128 sample_p_z = _mm_mul_ps(t, rays_dir_z);
        sample_p_x = _mm_add_ps(sample_p_x, rays_base_x);
        sample_p_y = _mm_add_ps(sample_p_y, rays_base_y);
        sample_p_z = _mm_add_ps(sample_p_z, rays_base_z);

        /* Map the sample position to a 2d (uv) point on the plane, so that we can sample a color */
        df_color color[4];
        for (int j = 0; j < 4; ++j) {
            float r = extract_float(sample_p_x, j);
            float g = extract_float(sample_p_y, j);
            
            printf("%f %f\n", r, g);
        }
    }

    /* Handle remaining (< 4) rays */
    if ((ray_count % 4) != 0) {
    
    }
}