目标：我正尝试在C中创建光线追踪器。我刚刚添加了一个光源，该光源应根据光线的位置为我的三个球体提供阴影效果。如果光在所有这些光的左侧，则应在右侧形成阴影。
问题：：更改灯光的强度和位置时，所有球体均会均匀更改。球体将或多或少被均匀照明，并且球体上各个像素的照明没有变化。
我的调试尝试：我尝试通过打印出许多不同的信息来查看变量输出，并且我认为源来自我的变量
diffuse_light_intensity
变化不大（在屏幕上的所有迭代中，由于表面上的光线角度变化很大，因此该值应经常变化时，该值会改变两次）
我的代码：（我的理论是问题出在scene_intersect（）或cast_ray（）上）
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <math.h>
#include <limits.h>
typedef struct {
float position[3];
float intensity;
} Light;
typedef struct {
float diffuse_color[3];
} Material;
typedef struct {
float center[3];
float radius;
Material material;
} Sphere;
int arrSub(const float arr1[], const float arr2[], float subArr[], int length) {
/*
Requires 3 equally sized arrays (denoted as length),
arr1 - arr2 will result in the third array subArr
*/
for (int i = 0; i < length; i++) {
subArr[i] = arr1[i] - arr2[i];
}
return 0;
}
int arrAdd(const float arr1[], const float arr2[], float addArr[], int length) {
/*
Requires 3 equally sized arrays (denoted as length),
arr1 + arr2 will result in the third array subArr
*/
for (int i = 0; i < length; i++) {
addArr[i] = arr1[i] + arr2[i];
}
return 0;
}
int arrScalarMult(const float arr1[], float scalar, float newArr[], int length) {
/*
Requires 3 equally sized arrays (denoted as length),
arr1 - arr2 will result in the third array subArr
*/
for (int i = 0; i < length; i++) {
newArr[i] = arr1[i] * scalar;
}
return 0;
}
float dotProduct(const float arr1[], const float arr2[], int length) {
/*
Returns the dot product of two equal sized arrays
(treated as vectors)
a (dot) b = a1b1 + a2b2 + ... anbn
*/
float result = 0;
for (int i = 0; i < length; i++) {
result += arr1[i] * arr2[i];
}
return result;
}
int normalize(float arr[], int len) {
//Normalize a vector (array)
float sumSqr;
float norm;
for (int i = 0; i < len; i++) {
sumSqr += arr[i] * arr[i];
}
norm = sqrt(sumSqr);
for (int i = 0; i < len; i++) {
arr[i] = arr[i] / norm;
}
return 0;
}
bool ray_intersect(const float origin[], const float dir[], float t0, Sphere s) {
/*
Ray-Sphere Intersection
Vectors:
origin (the zero vector)
dir (direction vector)
L (vector from origin to center of sphere)
Scalars:
tca
d2
thc
t0
t1
*/
float L[3] = {0,0,0}; //The zero vector
arrSub(s.center, origin, L, 3); //L is now the vector from origin to the sphere's center
float tca = dotProduct(L, dir, 3); //Projection of L onto dir
float d2 = dotProduct(L, L, 3) - tca*tca;
if (d2 > s.radius * s.radius) return false; //There is no intersection, so return false.
float thc = sqrtf((s.radius*s.radius - d2));
t0 = tca - thc;
float t1 = tca + thc;
if (t0 < 0) {
t0 = t1;
}
if (t0 < 0) return false;
return true;
}
bool scene_intersect(const float origin[], const float dir[], const Sphere s[], int len, float hit[], float N[], Material * ptr_m) {
float sphere_dist = INT_MAX;
for (size_t i=0; i < len; i++) {
float dist_i;
if (ray_intersect(origin, dir, dist_i, s[i]) && dist_i < sphere_dist) {
sphere_dist = dist_i;
float dirDist[3];
arrScalarMult(dir, dist_i, dirDist, 3);
arrAdd(origin, dirDist, hit, 3);
float hitMinusCenter[3];
arrSub(hit, s[i].center, hitMinusCenter, 3);
normalize(hitMinusCenter, 3);
N[0] = hitMinusCenter[0];
N[1] = hitMinusCenter[1];
N[2] = hitMinusCenter[2];
* ptr_m = s[i].material;
}
}
return sphere_dist<1000;
}
int cast_ray(const float origin[], const float dir[], const Sphere s[], const Light l[], int l_size, unsigned char colorArr[]) {
float point[3], N[3];
Material m;
Material * ptr_m = &m;
if (!scene_intersect(origin, dir, s, 3, point, N, ptr_m)) {
//background
colorArr[0] = 5; //red
colorArr[1] = 100; //green
colorArr[2] = 250; //blue
} else {
float diffuse_light_intensity = 0;
float light_dir[3];
for (size_t i = 0; i < l_size; i++) {
arrSub(l[i].position, point, light_dir, 3);
normalize(light_dir, 3);
diffuse_light_intensity += l[i].intensity * ((0.f >= dotProduct(light_dir, N, 3) ? (0.f) : (dotProduct(light_dir, N, 3))));
}
//light up pixel
colorArr[0] = m.diffuse_color[0] * diffuse_light_intensity;
colorArr[1] = m.diffuse_color[1] * diffuse_light_intensity;
colorArr[2] = m.diffuse_color[2] * diffuse_light_intensity;
}
return 0;
}
int render(const Sphere s[], const Light l[], int l_length) {
/*
Creates image in a new color each step.
*/
const int width = 1024;
const int height = 768;
FILE *fp = fopen("fourth.ppm", "wb"); // Write in binary mode
(void) fprintf(fp, "P6\n%d %d\n255\n", width, height);
float fov = 3.1415926535/2.; // Field of View
#pragma omp parallel for
for (size_t j = 0; j < height; j++) {
for (size_t i = 0; i < width; i++) {
float x = (2*(i+.5)/(float)width - 1)*tan(fov/2.)*width/(float)height;
float y = -(2*(j+.5)/(float)height - 1)*tan(fov/2.);
float dir[] = {x,y,-1};
normalize(dir, 3);
unsigned char color[3];
const float origin[] = {0,0,0};
cast_ray(origin, dir, s, l, l_length, color);
(void) fwrite(color, 1, 3, fp);
}
}
(void) fclose(fp);
return 0;
}
int main(void) {
Material red = {255,0,0};
Material pink = {150,10,150};
Material gold = {255, 195, 0};
//Populate with spheres
Sphere s[3];
Sphere originalS = {{-3,0,-16},2,gold};
Sphere bigS = {{-1.0, -1.5, -12}, 3, red};
Sphere anotherS = {{7,5,-18},2,pink};
s[0] = originalS;
s[1] = bigS;
s[2] = anotherS;
//Add light source
Light l[1];
Light test_light = {{-20,20,20}, 1.5};
l[0] = test_light;
render(s,l, 1);
printf("Run success!\n");
return 0;
}
如果需要对我的代码进行任何澄清，请告诉我，我对C和stackoverflow还是陌生的。
答案 0 :(得分：3)
在const example = (arg1, ...args) => {
console.log(arg1);
for (arg in args) {
console.log(arg);
}
}
中存在一个基本错误，在该错误中您按值传递ray_intersect变量，而不是将其作为指针，因此在t0函数中，其值始终为零。
另一个问题是您没有在scene_intersect函数中初始化sumSqr，导致该函数为每个矢量分量返回normalize。
固定这两个位置后，我得到一些近似阴影的球。该图像中的错误是由于无法确保您的输出像素值落在[0，255]范围内引起的。
NB：如果您打开完整的编译器错误检查，则会检测到这两个错误中的第一个 ，警告您正在使用未初始化的变量。