对于一个简单的2D游戏,我正在尝试使用矩阵围绕z轴旋转精灵。我显然做错了,因为当我试图旋转我的精灵时它看起来像是围绕屏幕原点(底部,左边)而不是精灵原点旋转。我很困惑,因为我的四边形已经在原点,所以我认为我不需要翻译 - >旋转并平移。这是代码段和小视频或erroneous transformation
void MatrixMultiply(
MATRIX &mOut,
const MATRIX &mA,
const MATRIX &mB);
/*!***************************************************************************
@Function TransTransformArray
@Output pTransformedVertex Destination for transformed vectors
@Input pV Input vector array
@Input nNumberOfVertices Number of vectors to transform
@Input pMatrix Matrix to transform the vectors of input vector (e.g. use 1 for position, 0 for normal)
@Description Transform all vertices in pVertex by pMatrix and store them in
pTransformedVertex
- pTransformedVertex is the pointer that will receive transformed vertices.
- pVertex is the pointer to untransformed object vertices.
- nNumberOfVertices is the number of vertices of the object.
- pMatrix is the matrix used to transform the object.
*****************************************************************************/
void TransTransformArray(
VECTOR3 * const pTransformedVertex,
const VECTOR3 * const pV,
const int nNumberOfVertices,
const MATRIX * const pMatrix);
RenderQuad CreateRenderQuad(
const Texture2D & texture,
float x,
float y,
float scaleX,
float scaleY,
float rotateRadians,
int zIndex,
const Color & color,
const Quad2 & textureCoord,
const char * name
) {
MATRIX mT;
MATRIX mS;
MATRIX concat;
MATRIX mR;
MatrixTranslation(mT, x, y, 0.0f);
MatrixRotationZ(mR, rotateRadians);
MatrixScaling(mS, scaleX, scaleY, 1.0f);
VECTOR3 quad[] = {
{-0.5f, 0.5f, 0.f}, //tl
{0.5f, 0.5f, 0.f}, //tr
{-0.5, -0.5f, 0.0f}, //bl
{0.5f, -0.5f, 0.0f}, //br
};
MatrixMultiply(concat, mR, mT);
MatrixMultiply(concat, concat, mS);
// apply to all the points in the quad
TransTransformArray(quad, quad, 4, &concat);
==更新:
这是结构和渲染代码:
我正在使用oolongengine中的矩阵类code.google.com/p/oolongengine/source/browse/trunk/Oolong%20Engine2/Math/Matrix.cpp
我转换所有四边形,然后使用OpenGL渲染它们。这是我的数据结构和渲染代码:
typedef struct _RenderData {
VECTOR3 vertex;
RenderColor3D color;
RenderTextureCoord textureCoord;
float zIndex;
GLuint textureId;
} RenderData;
typedef struct _RenderQuad {
//! top left
RenderData tl;
//! top right
RenderData tr;
//! bottom left
RenderData bl;
//! bottom right
RenderData br;
float zIndex;
Texture2D * texture; // render quad draws a source rect from here
ESpriteBlendMode blendMode;
} RenderQuad ;
/// Draw
class QuadBatch {
GLushort * m_indices;
const Texture2D * m_texture;
GLuint m_vbos[2];
RenderData * m_vertices;
};
QuadBatch::Draw () {
int offset = (int)&m_vertices[startIndex];
// vertex
int diff = offsetof( RenderData, vertex);
glVertexPointer(3, GL_FLOAT, kRenderDataSize, (void*) (offset + diff) );
// color
diff = offsetof( RenderData, color);
glColorPointer(4, GL_FLOAT, kRenderDataSize, (void*)(offset + diff));
// tex coords
diff = offsetof( RenderData, textureCoord);
glTexCoordPointer(2, GL_FLOAT, kRenderDataSize, (void*)(offset + diff));
// each quad has 6 indices
glDrawElements(GL_TRIANGLES, vertexCount * elementMultiplier, GL_UNSIGNED_SHORT, m_indices);
答案 0 :(得分:2)
x - > a + R(x-a)= Rx +(a-Ra)
(这可能需要一些盯着消化)。所以,在应用你的旋转之后 - 正如你所观察到的那样,在原点周围旋转 - 你必须添加常量向量(a - Ra)。
[编辑:]这个答案是语言和平台不可知的 - 无论你在哪里,数学都是一样的。特定库包含不同的结构和API以应用转换。例如,DirectX和OpenGL都保持4x4矩阵变换,将旋转和平移统一为单个矩阵乘法(通过称为齐次坐标的设备)。