在C++中检测2d碰撞

Question

我需要创建一个函数，如果两个精灵之间没有碰撞，则返回false，如果有，则返回true。我想了很长时间，找不到确切的解决方案，目标是检测每个像素是否有碰撞，也就是说，如果两个阿尔法值(来自rgba(不同于0(可见(的像素在空间中的同一位置重合，则函数具有以下特征：

bool checkPixelCollision(
const Vector2& pixelPos1, 
const Vector2& pixelSize1, 
const vector<uint8_t> pixel1, 
const Vector2& pixelPos2, 
const Vector2& pixelSize2, 
const vector<uint8_t> pixel2);

Vector2是一个具有下一个形式的结构：

struct Vector2
{
float x;
float y;
};

pixelPos1是包含子画面1的矩形左上角的位置，pixelSize1是包含子图像1的矩形的大小(x=宽度；y=高度(，pixel1是具有rgba值的矢量​​对于子画面的每个像素，它们从4存储到4，使得i包含像素i的r的量；i+1是像素i的g的量；i+2是像素i的b的量；i+3是像素i的α的量，因此如果i+3不同于0是可见像素，则pixel1的大小由pixelSize1.x*pixelSize 1.y*4给出。标题的其他三个参数是与子画面2相对应的参数。因此，目标是检查何时发生碰撞(在侧面或拐角处(，并从那里在两个矩形之间建立一个碰撞矩形(重合区域(，并设置行进pixel1和pixel2的两个索引(因为每个索引都必须从其对应向量中的不同位置开始(。问题是我找不到一个最佳和/或简单的方法来做这件事，而且它是有效的。如果有人知道怎么做，我将不胜感激。

编辑这是我的代码(不起作用(

#include <algorithm>
#include <stdint.h>
#include <vector>
struct Vector2
{
float x;
float y;
};
float clamp(float val, float min, float max) {
return std::max(min, std::min(max, val));
}
bool checkPixelCollision(const Vector2& pixelPos1, const Vector2& pixelSize1, const vector<uint8_t> pixel1, const Vector2& pixelPos2, const Vector2& pixelSize2, const vector<uint8_t> pixel2) {
return check(pixelPos1,pixelSize1,pixel1,pixelPos2,pixelSize2,pixel2)||check(pixelPos2,pixelSize2,pixel2,pixelPos1,pixelSize1,pixel1);
}
bool check(const Vector2& pixelsPos1, const Vector2& pixelsSize1, const vector<uint8_t> pixels1, const Vector2& pixelsPos2, const Vector2& pixelsSize2, const vector<uint8_t> pixels2){
bool res = false;
if (pixelsPos1.x <= pixelsPos2.x + pixelsSize2.x && pixelsPos1.y <= pixelsPos2.y + pixelsSize2.y && pixelsPos1.x >= pixelsPos2.x && pixelsPos1.y >= pixelsPos2.y) {
float i = pixelsSize2.x - (pixelsSize1.y*((pixelsPos1.x - pixelsPos2.x + pixelsSize2.x) / pixelsSize1.x));
float j = pixelsSize2.y - (pixelsSize1.y*((pixelsPos1.y - pixelsPos2.y + pixelsSize2.y) / pixelsSize1.y));
float ifin = fmin(pixelsSize1.x - pixelsSize2.x, pixelsSize1.x);
float jfin = fmin(pixelsSize1.y - pixelsSize2.y, pixelsSize1.y);
float i2 = 0;
float j2 = 0;
while (j<jfin-1) {
int k = floor((pixelsSize2.x*j) + i) * 4 - 1;
int k2 = floor((pixelsSize1.x*j2) + i2) * 4 - 1;
if (pixels1[k2 + 3] != 0 && pixels2[k + 3] != 0) {
res = true;
}
if (i < ifin) {
i = i + 1;
i2 = i2 + 1;
}
else {
i2 = 0;
i = pixelsSize2.x - (pixelsSize1.x*((pixelsPos1.x - pixelsPos2.x + pixelsSize2.x) / pixelsSize1.x));
j = j + 1;
j2 = j2 + 1;
}
}
}
else if (pixelsPos1.x <= pixelsPos2.x + pixelsSize2.x && pixelsPos1.y + pixelsSize1.y >= pixelsPos2.y && pixelsPos1.x >= pixelsPos2.x && pixelsPos1.y + pixelsSize1.y <= pixelsPos2.y + pixelsSize2.y) {
float i = clamp(pixelsSize2.x - (pixelsSize1.x*((pixelsPos1.x - pixelsPos2.x + pixelsSize2.x) / pixelsSize1.x)), 0.0f, pixelsSize2.x);
float jfin = clamp(pixelsSize1.y*((pixelsPos2.y - pixelsPos1.y+pixelsSize1.y) / pixelsSize1.y), 0.0f, pixelsSize1.y);
float ifin = fmin(pixelsSize1.x - pixelsSize2.x, pixelsSize1.x);
float j = 0;
float i2 = 0;
float j2 = clamp(pixelsSize1.y - pixelsSize1.y*((pixelsPos2.y - pixelsPos1.y + pixelsSize1.y) / pixelsSize1.y),0.0f, pixelsSize1.y);
while (j<jfin-1) {
int k = floor((pixelsSize2.x*j) + i) * 4 - 1;
int k2 = floor((pixelsSize1.x*j2) + i2) * 4 - 1;
if (pixels1[k2 + 3] != 0 && pixels2[k + 3] != 0) {
res = true;
}
if (i < ifin) {
i = i + 1;
i2 = i2 + 1;
}
else {
i2 = 0;
i = clamp(pixelsSize2.x - (pixelsSize1.x*((pixelsPos1.x - pixelsPos2.x + pixelsSize2.x) / pixelsSize1.x)),0.0f, pixelsSize2.x);
j = j + 1;
j2 = j2 + 1;
}
}
}
else if (pixelsPos1.x + pixelsSize1.x >= pixelsPos2.x && pixelsPos1.y<= pixelsPos2.y + pixelsSize2.y && pixelsPos1.x + pixelsSize1.x <= pixelsPos2.x + pixelsSize2.x && pixelsPos1.y >= pixelsPos2.y) {
float ifin = clamp(pixelsSize1.x*((pixelsPos2.x - pixelsPos1.x + pixelsSize1.x) / pixelsSize1.x), 0.0f, pixelsSize1.x);
float j = clamp(pixelsSize2.y - (pixelsSize1.y*((pixelsPos1.y - pixelsPos2.y + pixelsSize2.y) / pixelsSize1.y)),0.0f, pixelsSize2.y);
float jfin = fmin(pixelsSize1.y - pixelsSize2.y, pixelsSize1.y);
float i = 0;
float i2 = clamp(pixelsSize1.x - pixelsSize1.x*((pixelsPos2.x - pixelsPos1.x + pixelsSize1.x) / pixelsSize1.x), 0.0f, pixelsSize1.x);
float j2 = 0;
while (j<jfin-1) {
int k = floor((pixelsSize2.x*j) + i) * 4 - 1;
int k2 = floor((pixelsSize1.x*j2) + i2) * 4 - 1;
if (pixels1[k2 + 3] != 0 && pixels2[k + 3] != 0) {
res = true;
}
if (i < ifin) {
i = i + 1;
i2 = i2 + 1;
}
else {
i2 = clamp(pixelsSize1.x - pixelsSize1.x*((pixelsPos2.x - pixelsPos1.x + pixelsSize1.x) / pixelsSize1.x), 0.0f, pixelsSize1.x);
i = 0;
j = j + 1;
j2 = j2 + 1;
}
}
}
else if (pixelsPos1.x + pixelsSize1.x >= pixelsPos2.x && pixelsPos1.y + pixelsSize1.y >= pixelsPos2.y && pixelsPos1.x + pixelsSize1.x <= pixelsPos2.x + pixelsSize2.x && pixelsPos1.y + pixelsSize1.y <= pixelsPos2.y + pixelsSize2.y) {
float jfin = clamp(pixelsSize1.y*((pixelsPos2.y - pixelsPos1.y + pixelsSize1.y) / pixelsSize1.y), 0.0f, pixelsSize1.y);
float j = 0;
float ifin = clamp(pixelsSize1.x*((pixelsPos2.x - pixelsPos1.x + pixelsSize1.x) / pixelsSize1.x), 0.0f, pixelsSize1.x);
float i = 0;
float i2 = clamp(pixelsSize1.x - pixelsSize1.x*((pixelsPos2.x - pixelsPos1.x + pixelsSize1.x) / pixelsSize1.x), 0.0f, pixelsSize1.x);
float j2 = clamp(pixelsSize1.y - pixelsSize1.y*((pixelsPos2.y - pixelsPos1.y + pixelsSize1.y) / pixelsSize1.y), 0.0f, pixelsSize1.y);
while (j<jfin-1) {
int k = floor((pixelsSize2.x*j) + i) * 4 - 1;
int k2 = floor((pixelsSize1.x*j2) + i2) * 4 - 1;
if (pixels1[k2 + 3] != 0 && pixels2[k + 3] != 0) {
res = true;
}
if (i < ifin) {
i = i + 1;
i2 = i2 + 1;
}
else {
i2 = clamp(pixelsSize1.x - pixelsSize1.x*((pixelsPos2.x - pixelsPos1.x + pixelsSize1.x) / pixelsSize1.x), 0.0f, pixelsSize1.x);
i = 0;
j = j + 1;
j2 = j2 + 1;
}
}
}
return res;
}

Answer 1

首先检查两个精灵的边界矩形是否重叠。如果他们不这样做，那就太好了；不可能发生碰撞。如果它们确实重叠，计算每个精灵的重叠矩形，并逐像素进行比较——如果像素a或像素b是透明的，则该像素不会引起碰撞，如果两个像素都是不透明的，则会发生碰撞，您就完成了。如果完成了对重叠区域中所有像素的检查，并且没有碰撞，则也完成了检查。