我在GameBoyAdvance上编写了一个简单的自上而下的汽车驾驶游戏，类似于第一个GTA。我只使用矢量图形这样做，GBA不能很好地处理它;基本上有5个行人实例滞后。
我在优化代码方面没有太多经验，所以我想知道是否可以对我的代码进行一些调整以使其运行得更快，而不是取决于它在GBA上运行的事实
我使用的碰撞测试是SAT（分离轴定理），因为我发现它是用矢量图形进行碰撞检查的最简单的;游戏本身很简单。
以下是代码：
/*
GTA Vector City
Author: Alberto Taiuti
Version: 2.0
*/
#include "Global.h"
#include <string.h>
#include <cstdio>
#include "font.h"
#include "CVector2D.h"
#include "CCar.h"
#include "CPed.h"
#include <vector>
#include <memory>
/* GLOBAL VARIABLES */
void CheckCollisionsRect(CRect *test_a, CRect *test_b);
std::vector<CVector2D> PrepVectors(CRect *shape);
CVector2D GetMinMaxShape(std::vector<CVector2D> vect_shape, CVector2D axis);
void CheckCollisionRectVSPoint(CRect *test_a, CVector2D *point);
/* MAIN */
// The entry point for the game
int main()
{
// Frame counter
uint32_t frames = 0;
// Previous & current buttons states
static uint16_t prev_buttons = 0, cur_buttons = 0;
// Put the display into bitmap mode 3, and enable background 2.
REG_DISPCNT = MODE4 | BG2_ENABLE;
// Set up the palette.
SetPaletteBG(BLACK, RGB(0, 0, 0)); // black
SetPaletteBG(WHITE, RGB(31, 31, 31)); // white
SetPaletteBG(GREY, RGB(15, 15, 15)); // grey
SetPaletteBG(RED, RGB(31, 0, 0)); // red
SetPaletteBG(GREEN, RGB(0, 31, 0)); // green
SetPaletteBG(BLUE, RGB(0, 0, 31)); // blue
// Create car instance
CCar *car = new CCar(50,50);
// Create a building
/*CRect *test_b = new CRect(100.0f, 100.0f, 30, 30);
CRect *test_c = new CRect(120.0f, 120.0f, 30, 30);
CRect *test_d = new CRect(30.0f, 30.0f, 30, 30);*/
// Pedestrian instances
int ped_number = 10; // Number of pedestrians
std::vector<CPed*> peds; // Ped. entities container (made of smart pointers)
typedef std::vector<CPed*>::iterator p_itor; // Iterator
for(int i = 1; i <= ped_number; i++)
{
peds.push_back(new CPed(i, RED, 2.0f));
}
// Check whether the game is over
bool end = false;
// Main loop
while (!end)
{
// Flip the screen
FlipBuffers();
//Clear the screen
ClearScreen8(BLACK);
// Update frame counter
frames ++;
// Get the current state of the buttons.
cur_buttons = REG_KEYINPUT;
// Handle Input
car->HandleInput(prev_buttons, cur_buttons);
// Logic
car->Update();
for(int i = 0; i < ped_number; i++)
{
peds[i]->Update();
}
for(int i = 0; i < ped_number; i++)
{
CheckCollisionRectVSPoint(car->shape, peds[i]->pos);
}
/*CheckCollisionsRect(car->shape, test_b);
CheckCollisionsRect(car->shape, test_c);
CheckCollisionsRect(car->shape, test_d);
CheckCollisionRectVSPoint(car->shape, test_ped->pos);*/
// Render
car->Draw();
for(int i = 0; i < ped_number; i++)
{
peds[i]->Draw();
}
/*test_b->DrawFrame8(GREEN);
test_c->DrawFrame8(WHITE);
test_d->DrawFrame8(RED);
test_ped->Draw();*/
prev_buttons = cur_buttons;
// VSync
WaitVSync();
}
// Free memory
delete car;
//delete test_b; delete test_c; delete test_d;
//delete test_ped;
for(p_itor itor = peds.begin(); itor != peds.end(); itor ++)// Delete pedestrians
{
peds.erase(itor);
}
return 0;
}
void CheckCollisionsRect(CRect *test_a, CRect *test_b)
{
// If the two shapes are close enough, check for collision, otherways skip and save calculations to the CPU
//if((pow((test_a->points[0]->x - test_b->points[0]->x), 2) + pow((test_a->points[0]->y - test_b->points[0]->y), 2)) < 25.0f)
{
// Prepare the normals for both shapes
std::vector<CVector2D> normals_a = test_a->GetNormalsAsArray();
std::vector<CVector2D> normals_b = test_b->GetNormalsAsArray();
// Create two containers for holding the various vectors used for collision check
std::vector<CVector2D> vect_test_a = PrepVectors(test_a);
std::vector<CVector2D> vect_test_b = PrepVectors(test_b);
// Get the min and max vectors for each shape for each projection (needed for SAT)
CVector2D result_P1 = GetMinMaxShape(vect_test_a, normals_a[1]); //
CVector2D result_P2 = GetMinMaxShape(vect_test_b, normals_a[1]); //
// If the two objects are not colliding
if(result_P1.y < result_P2.x || result_P2.y < result_P1.x)
{
return;
}
CVector2D result_Q1 = GetMinMaxShape(vect_test_a, normals_a[0]); // First axis couple
CVector2D result_Q2 = GetMinMaxShape(vect_test_b, normals_a[0]); //
if(result_Q1.y < result_Q2.x || result_Q2.y < result_Q1.x)
{
return;
}
CVector2D result_R1 = GetMinMaxShape(vect_test_a, normals_b[1]); //
CVector2D result_R2 = GetMinMaxShape(vect_test_b, normals_b[1]); //
if(result_R1.y < result_R2.x || result_R2.y < result_R1.x)
{
return;
}
CVector2D result_S1 = GetMinMaxShape(vect_test_a, normals_b[0]); // Second axis couple
CVector2D result_S2 = GetMinMaxShape(vect_test_b, normals_b[0]); //
if(result_S1.y < result_S2.x || result_S2.y < result_S1.x)
{
return;
}
// Do something
PlotPixel8(200, 10, WHITE);
PlotPixel8(200, 11, WHITE);
PlotPixel8(200, 12, WHITE);
}
}
// Check for collision between an OOBB and a point
void CheckCollisionRectVSPoint(CRect *test_a, CVector2D *point)
{
// Prepare the normals for the shape
std::vector<CVector2D> normals_a = test_a->GetNormalsAsArray();
// Create a container for holding the various vectors used for collision check
std::vector<CVector2D> vect_test_a = PrepVectors(test_a);
// Get projections for the OOBB (needed for SAT)
CVector2D result_P1 = GetMinMaxShape(vect_test_a, normals_a[1]);
float result_point = point->DotProduct(normals_a[1]);
// If the two objects are not colliding on this axis
if(result_P1.y < result_point || result_point < result_P1.x)
{
return;
}
CVector2D result_Q1 = GetMinMaxShape(vect_test_a, normals_a[0]);
result_point = point->DotProduct(normals_a[0]);
// If the two objects are not colliding on this axis
if(result_Q1.y < result_point || result_point < result_Q1.x)
{
return;
}
// Do something
PlotPixel8(200, 10, WHITE);
PlotPixel8(200, 11, WHITE);
PlotPixel8(200, 12, WHITE);
}
// Returns a container with projection vectors for a given shape
std::vector<CVector2D> PrepVectors(CRect *shape)
{
std::vector<CVector2D> vect;
// Create vectors for projection and load them into the arrays
for( uint16_t i=0; i < 5; i++)
{
// Get global position of vectors and then add them to the array
vect.push_back(shape->GetVectorGlobal(i));
}
return vect;
}
CVector2D GetMinMaxShape(std::vector<CVector2D> vect_shape, CVector2D axis)
{
// Set initial minimum and maximum for shape's projection vectors
float min_proj = vect_shape[1].DotProduct(axis);
float max_proj = vect_shape[1].DotProduct(axis);
// Calculate max and min projection vectors by iterating along all of the corners
for(uint16_t i = 2; i < vect_shape.size(); i ++)
{
float current_proj = vect_shape[i].DotProduct(axis);
// Select minimum projection on axis
if(current_proj < min_proj) // If current projection is smaller than the minimum one
min_proj = current_proj;
// Select maximum projection on axis
if(current_proj > max_proj) // If current projection is greater than the minimum one
max_proj = current_proj;
}
return (CVector2D(min_proj, max_proj)); // Return a vector2D as it is a handy way for returning a couple of values
}
非常感谢大家，对于凌乱的代码感到抱歉！
答案 0 :(得分：1)
我给了它一个非常快速的阅读，所以我可能忽略了一些东西。嗯，有一些明显的提高性能的技巧，例如通过引用将向量传递给函数。使用前缀增量而不是后缀也是一个好习惯。这两条规则绝对不像'过早优化，......的根源'。不要逐个删除行人，而是使用std::vector::clear().并且如果你声称使用智能指针，那么你应该说，因为你没有删除行人指针，因为它似乎有内存泄漏。尽可能使用const关键字。一旦你进行了明显的修正，并且速度仍然不能令人满意，那么你需要使用分析器。
阅读有关优化的内容，例如：http://www.agner.org/optimize/optimizing_cpp.pdf
答案 1 :(得分：0)
有一件事在我身上跳了出来（除了通过价值而不是参考不断传递向量，这将是非常昂贵的！）
在你的碰撞检测中，你会看到汽车是否撞到每个行人
for(int i = 0; i < ped_number; i++)
{
CheckCollisionRectVSPoint(car->shape, peds[i]->pos);
}
然后，在碰撞检测器中，您每次都会对汽车形状重复进行大量相同的处理： -
// Prepare the normals for both shapes
std::vector<CVector2D> normals_a = test_a->GetNormalsAsArray();
// Create two containers for holding the various vectors used for collision check
std::vector<CVector2D> vect_test_a = PrepVectors(test_a);
......等......
你应该重做那个循环来为一次创建汽车的法线等，然后对每个行人重复使用每次检查的结果。