粒子特效编程与手机应用研究

<!-- [if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:DrawingGridVerticalSpacing>7.8 磅</w:DrawingGridVerticalSpacing> <w:DisplayHorizontalDrawingGridEvery>0</w:DisplayHorizontalDrawingGridEvery> <w:DisplayVerticalDrawingGridEvery>2</w:DisplayVerticalDrawingGridEvery> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:SpaceForUL/> <w:BalanceSingleByteDoubleByteWidth/> <w:DoNotLeaveBackslashAlone/> <w:ULTrailSpace/> <w:DoNotExpandShiftReturn/> <w:AdjustLineHeightInTable/> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> <w:UseFELayout/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!-- [if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--><!-- [if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:普通表格; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]-->

<!-- [if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:DrawingGridVerticalSpacing>7.8 磅</w:DrawingGridVerticalSpacing> <w:DisplayHorizontalDrawingGridEvery>0</w:DisplayHorizontalDrawingGridEvery> <w:DisplayVerticalDrawingGridEvery>2</w:DisplayVerticalDrawingGridEvery> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:SpaceForUL/> <w:BalanceSingleByteDoubleByteWidth/> <w:DoNotLeaveBackslashAlone/> <w:ULTrailSpace/> <w:DoNotExpandShiftReturn/> <w:AdjustLineHeightInTable/> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> <w:UseFELayout/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!-- [if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--><!-- [if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:普通表格; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]-->

粒子系统于 1983 年由 reeves 提出 ，最初它并不是针对非刚性物体的建模而提出，它是为了解决对一些自然现象和自然景物的模拟而产生的，如雨，雪，雾，水波，火焰，焰火，烟尘，流星等自然现象，后来才逐渐的用于对非刚性的物体建模之中。

构成物体的物质都是由基本粒子构成，水由水分子构成，烟雾由气体分子和尘埃构成，火焰由光子和空气微粒构成，研究这些构成物质的粒子的状态和运动方式，并建立相应的物理模型，就可以用计算机模拟出相应的自然现象。粒子系统的方法就是将大量的粒子单元集合在一起，通过其属性的变化表现物体的物理特性的物体模拟方法。每个粒子是有着形状大小颜色透明度位置及速度等属性的几何单元，一个粒子究竟有什么样的属性主要取决于具体的应用。粒子系统不是一个简单的静态系统，随着时间的推移，系统中已有的粒子不仅不断改变形状，不断运动，而且不断有新的粒子加入，并有旧粒子的消失，这样才能演示出我们这个变幻万千，生机勃勃的世界。而粒子与我们显示设备中的像素具有一定的相通相似性。利用一个或者多个像素构造粒子，再赋予粒子各种属性，状态，运行轨迹，把成百上千个同样的粒子组合起来，利用随机函数，程序员有时可以创造出令艺术家都惊叹的视觉效果。

最近在网上阅读突然对粒子起了兴趣，趁空闲时研究了一下网上有关粒子编程的水波，火焰，下雪效果，按照相应的算法，写出相应的手机算法，初期效果不理想，后期根据相应手机平台优化后，运行速度得到极大提升，在某些情况下，我不得不使用 TIMER 延缓每帧播放的速度。

三种效果，水波的模拟运算量最高，火焰次之，下雪最少。下雪特效使用了网上通用的算法，几乎不做优化就能使用。我做的工作主要在于单个雪花形状的渲染，通过设计不同形状，不同大小，不同水平升垂直速度的雪花，体现某种空间感。使用 FOR 循环随机为雪花赋值坐标，橫向速度，纵向速度，生命周期，不同大小的雪花可以形成空间层次感，速度的不同可以表现出雪花随风的动态，雪花生命周期结束时停留下来生成雪地。这个程序也可以模拟落叶和落花效果和下雨效果，就是更改一下横向的速度，落叶和落花由于空气浮力的存在，在下落上会表现的更大的横向飘移，雨的纵向速度要比横向更大一些，而且偏移方向更一致一些。效果如下，左边是原图，右边是加入了飞落雪花的效果。

<!-- [if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:DrawingGridVerticalSpacing>7.8 磅</w:DrawingGridVerticalSpacing> <w:DisplayHorizontalDrawingGridEvery>0</w:DisplayHorizontalDrawingGridEvery> <w:DisplayVerticalDrawingGridEvery>2</w:DisplayVerticalDrawingGridEvery> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:SpaceForUL/> <w:BalanceSingleByteDoubleByteWidth/> <w:DoNotLeaveBackslashAlone/> <w:ULTrailSpace/> <w:DoNotExpandShiftReturn/> <w:AdjustLineHeightInTable/> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> <w:UseFELayout/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!-- [if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--><!-- [if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:普通表格; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]-->雪花渲染如下：

<!-- [if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:DrawingGridVerticalSpacing>7.8 磅</w:DrawingGridVerticalSpacing> <w:DisplayHorizontalDrawingGridEvery>0</w:DisplayHorizontalDrawingGridEvery> <w:DisplayVerticalDrawingGridEvery>2</w:DisplayVerticalDrawingGridEvery> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:SpaceForUL/> <w:BalanceSingleByteDoubleByteWidth/> <w:DoNotLeaveBackslashAlone/> <w:ULTrailSpace/> <w:DoNotExpandShiftReturn/> <w:AdjustLineHeightInTable/> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> <w:UseFELayout/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!-- [if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--><!-- [if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:普通表格; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]-->

void drawonwsnow(S32 x, S32 y, gdi_color c)

{

switch (rand()%16)

{

case 0:

gdi_act_put_pixel(x, y, c);

break;

case 1:

gdi_act_put_pixel(x, y, c);

gdi_act_put_pixel(x-1, y, c);

break;

case 2:

gdi_act_put_pixel(x, y, c);

gdi_act_put_pixel(y-1, y, c);

break;

case 3:

gdi_act_put_pixel(x, y, c);

gdi_act_put_pixel(x-1, y, c);

gdi_act_put_pixel(x+1, y, c);

break;

case 4:

gdi_act_put_pixel(x, y, c);

gdi_act_put_pixel(x, y-1, c);

gdi_act_put_pixel(x, y+1, c);

break;

case 5:

gdi_act_put_pixel(x, y, c);

gdi_act_put_pixel(x+1, y, c);

gdi_act_put_pixel(x, y-1, c);

gdi_act_put_pixel(x, y+1, c);

break;

case 6:

gdi_act_put_pixel(x, y, c);

gdi_act_put_pixel(x-1, y, c);

gdi_act_put_pixel(x, y-1, c);

gdi_act_put_pixel(x, y+1, c);

break;

case 7:

gdi_act_put_pixel(x, y, c);

gdi_act_put_pixel(x-1, y, c);

gdi_act_put_pixel(x+1, y, c);

gdi_act_put_pixel(x, y-1, c);

break;

case 8:

gdi_act_put_pixel(x, y, c);

gdi_act_put_pixel(x-1, y, c);

gdi_act_put_pixel(x+1, y, c);

gdi_act_put_pixel(x, y+1, c);

break;

case 9:

gdi_act_put_pixel(x, y, c);

gdi_act_put_pixel(x-1, y, c);

gdi_act_put_pixel(x+1, y, c);

gdi_act_put_pixel(x, y-1, c);

gdi_act_put_pixel(x, y+1, c);

break;

case 10:

gdi_act_put_pixel(x, y, c);

gdi_act_put_pixel(x-1, y, c);

gdi_act_put_pixel(x+1, y, c);

gdi_act_put_pixel(x, y-1, c);

gdi_act_put_pixel(x, y+1, c);

gdi_act_put_pixel(x-1, y-1, c);

gdi_act_put_pixel(x+1, y+1, c);

gdi_act_put_pixel(x+1, y-1, c);

gdi_act_put_pixel(x-1, y+1, c);

break;

case 11:

gdi_act_put_pixel(x, y, c);

gdi_act_put_pixel(x-1, y, c);

gdi_act_put_pixel(x+1, y, c);

gdi_act_put_pixel(x, y-1, c);

gdi_act_put_pixel(x, y+1, c);

gdi_act_put_pixel(x-1, y-1, c);

gdi_act_put_pixel(x+1, y+1, c);

gdi_act_put_pixel(x+1, y-1, c);

gdi_act_put_pixel(x-1, y+1, c);

gdi_act_put_pixel(x-2, y, c);

break;

case 12:

gdi_act_put_pixel(x, y, c);

gdi_act_put_pixel(x-1, y, c);

gdi_act_put_pixel(x+1, y, c);

gdi_act_put_pixel(x, y-1, c);

gdi_act_put_pixel(x, y+1, c);

gdi_act_put_pixel(x-1, y-1, c);

gdi_act_put_pixel(x+1, y+1, c);

gdi_act_put_pixel(x+1, y-1, c);

gdi_act_put_pixel(x-1, y+1, c);

gdi_act_put_pixel(x+2, y, c);

break;

case 13:

gdi_act_put_pixel(x, y, c);

gdi_act_put_pixel(x-1, y, c);

gdi_act_put_pixel(x+1, y, c);

gdi_act_put_pixel(x, y-1, c);

gdi_act_put_pixel(x, y+1, c);

gdi_act_put_pixel(x-1, y-1, c);

gdi_act_put_pixel(x+1, y+1, c);

gdi_act_put_pixel(x+1, y-1, c);

gdi_act_put_pixel(x-1, y+1, c);

gdi_act_put_pixel(x, y-2, c);

break;

case 14:

gdi_act_put_pixel(x, y, c);

gdi_act_put_pixel(x-1, y, c);

gdi_act_put_pixel(x+1, y, c);

gdi_act_put_pixel(x, y-1, c);

gdi_act_put_pixel(x, y+1, c);

gdi_act_put_pixel(x-1, y-1, c);

gdi_act_put_pixel(x+1, y+1, c);

gdi_act_put_pixel(x+1, y-1, c);

gdi_act_put_pixel(x-1, y+1, c);

gdi_act_put_pixel(x, y+2, c);

break;

case 15:

gdi_act_put_pixel(x, y, c);

gdi_act_put_pixel(x-1, y, c);

gdi_act_put_pixel(x+1, y, c);

gdi_act_put_pixel(x, y-1, c);

gdi_act_put_pixel(x, y+1, c);

gdi_act_put_pixel(x-1, y-1, c);

gdi_act_put_pixel(x+1, y+1, c);

gdi_act_put_pixel(x+1, y-1, c);

gdi_act_put_pixel(x-1, y+1, c);

gdi_act_put_pixel(x, y+2, c);

gdi_act_put_pixel(x, y-2, c);

gdi_act_put_pixel(x+2, y, c);

gdi_act_put_pixel(x-2, y, c);

break;

default:

gdi_act_put_pixel(x, y, c);

gdi_act_put_pixel(x-1, y, c);

gdi_act_put_pixel(x+1, y, c);

gdi_act_put_pixel(x, y-1, c);

gdi_act_put_pixel(x, y+1, c);

break;

}

}

<!-- [if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:DrawingGridVerticalSpacing>7.8 磅</w:DrawingGridVerticalSpacing> <w:DisplayHorizontalDrawingGridEvery>0</w:DisplayHorizontalDrawingGridEvery> <w:DisplayVerticalDrawingGridEvery>2</w:DisplayVerticalDrawingGridEvery> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:SpaceForUL/> <w:BalanceSingleByteDoubleByteWidth/> <w:DoNotLeaveBackslashAlone/> <w:ULTrailSpace/> <w:DoNotExpandShiftReturn/> <w:AdjustLineHeightInTable/> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> <w:UseFELayout/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!-- [if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--><!-- [if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:普通表格; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]-->

而对于火焰来说，就没有那么幸运，每一帧差不多要对一个完整的屏幕大小的数据 BUFFER 运算赋值，这使得他的渲染不能再使用 gdi_act_put_pixel 直接赋值，需要直接修改单个屏幕层的 BUFFER 来实现。火焰算法网上有很多，这里不多讲解：

1. 放置火源

for(x=0;x<blue_w-1;x++)

{

//srand(time(NULL));

fire[blue_h-1][x]=rand()%256;

}

2 ．火焰上升，原本要除以四，考虑到火焰衰减，这里从乘以 1000 ，除以 3925 得到，主要用于优化速度，避免除以一个浮点数降低程序的效率。

fire[y][x]=(S32)(((fire[y][x]+fire[y+1][x-1]+fire[y+1][x+1]+fire[y+1][x])*1000)/3925)%256;

左边是小火，右边是加入了衰减后的大火，可以渲染整个窗口

<!-- [if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:DrawingGridVerticalSpacing>7.8 磅</w:DrawingGridVerticalSpacing> <w:DisplayHorizontalDrawingGridEvery>0</w:DisplayHorizontalDrawingGridEvery> <w:DisplayVerticalDrawingGridEvery>2</w:DisplayVerticalDrawingGridEvery> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:SpaceForUL/> <w:BalanceSingleByteDoubleByteWidth/> <w:DoNotLeaveBackslashAlone/> <w:ULTrailSpace/> <w:DoNotExpandShiftReturn/> <w:AdjustLineHeightInTable/> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> <w:UseFELayout/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!-- [if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--><!-- [if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:普通表格; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]-->

对于水波算法，网上也有很多，主要是考虑到折射和衰减，其运算量大约相当于三到四屏次数的运算，为了优化算法，达到每秒十帧到二十帧。算法的优化是必不可少的，最重要的还是渲染，水波详细算法可以在网上看到，首先和火焰一样，放置波源：

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1 ．放置波源

// 加入波源

void DropStone(S32 x,S32 y, U16 stonesize, U8 stoneweight)

{

S32 posx, posy;

if ((x + stonesize) > MY_WATER_W || (y+stonesize) > MY_WATER_H ||

(x-stonesize)<0 ||(y-stonesize)<0)

{

return;

}

for (posx = x - stonesize; posx < x+stonesize; posx++)

{

for (posy = y-stonesize; posy < y+stonesize; posy++)

{

if ((posx-x)*(posx-x) + (posy-y)*(posy-y) < stonesize*stonesize)

{

my_water_buf1[MY_WATER_W*posy+posx] = -stoneweight;

}

}

}

}

2 ．计算缓冲区，这段代码出于效率考虑，我对他做了优化，比网上的多了一些代码，细心的朋友很快就能发现

// 计算缓冲区

void RippleSpread()

{

S32 i, j;

char * p;

if (isrun)

{

for (i=MY_WATER_W; i<MY_WATER_W*MY_WATER_H-MY_WATER_W; i++)

{

// 波能扩散

my_water_buf2[i] = ((my_water_buf1[i-1]+

my_water_buf1[i+1]+

my_water_buf1[i-MY_WATER_W]+

my_water_buf1[i+MY_WATER_W])

>>1)

- my_water_buf2[i];

// 波能衰减

my_water_buf2[i] -= my_water_buf2[i]>>5;

}

p = my_water_buf1;

my_water_buf1 = my_water_buf2;

my_water_buf2 = p;

for (i=0; i<MY_WATER_W*MY_WATER_H; i++)

{

isrun = FALSE;

if (my_water_buf1[i] != 0)

{

isrun = TRUE;

break;

}

}

}

}

4 ．渲染屏幕，这一步是很简单的，和网上是差不多的，直接拉来也可以使用，只是效率低一些，自己简单优化一下就会有很好的效率。