我在 OpenGL 内部围绕 x 轴的任何旋转都有一点问题。我所拥有的是一个在着色器内部渲染的基本立方体，带有用于照明计算的法线。立方体的变换是投影矩阵乘以模型矩阵。这种连接是在着色器中完成的，而旋转和平移计算是在我编写的 Matrix 类中完成的。当围绕 y 轴进行任何旋转时，一切都按预期旋转，如下图所示：
当围绕 x 轴发生任何旋转时，问题就开始了，如下所示：
显然，x 轴旋转会扭曲场景并导致一切显示不成比例。这是每次渲染时计算矩阵并传递给着色器的代码：
glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
viewMatrix.setIdentity();
viewMatrix.translate(new Vector4(translation));
viewMatrix.rotate(1, 0, 0, -rotateX);
viewMatrix.rotate(0, 1, 0, rotateY);
Matrix4 mvMatrix = new Matrix4(viewMatrix);
Matrix4 pMatrix = new Matrix4(projectionMatrix);
lightShader.useShader();
lightShader.setUniformVector("vColor", new Vector4(.4f,0,0,1f));
lightShader.setUniformMatrix("mvMatrix", mvMatrix);
lightShader.setUniformMatrix("pMatrix", pMatrix);
triangleBatch.draw(lightShader.getAttributes());
Display.update();
着色器代码如下：
uniform mat4 mvMatrix;
uniform mat4 pMatrix;
uniform vec4 vColor;
varying vec4 outFragColor;
attribute vec4 inVertex;
attribute vec4 inNormal;
void main(void) {
vec3 newNorm = vec3(inNormal);
mat3 mNormalMatrix;
mNormalMatrix[0] = mvMatrix[0].xyz;
mNormalMatrix[1] = mvMatrix[1].xyz;
mNormalMatrix[2] = mvMatrix[2].xyz;
vec3 vNorm = normalize(mNormalMatrix * newNorm);
vec3 vLightDir = vec3(0.0, 0.0, 1.0);
float fDot = max(0.0, dot(vNorm, vLightDir));
outFragColor.rgb = vColor.rgb * fDot;
outFragColor.a = vColor.a;
mat4 mvpMatrix;
mvpMatrix = pMatrix * mvMatrix;
gl_Position = mvpMatrix * inVertex;
}
最后，旋转的矩阵数学代码如下：
public Matrix4 rotate(Vector4 a, float radians){
Matrix4 temp = new Matrix4().setToRotate(a, radians);
this.multiply(temp);
return this;
}
public Matrix4 setToRotate(Vector4 a, float radians){
a = new Vector4(a).normalise();
float c = GameMath.cos(radians);
float s = GameMath.sin(radians);
float t = 1-c;
float x = a.x;
float y = a.y;
float z = a.z;
float x2 = a.x*a.x;
float y2 = a.y*a.y;
float z2 = a.z*a.z;
this.setIdentity();
this.matrix[0] = c + t*x2;
this.matrix[1] = t*x*y + s*z;
this.matrix[2] = t*x*z - s*y;
this.matrix[4] = t*x*y - s*z;
this.matrix[5] = c + t*y2;
this.matrix[6] = t*y*z + s*x;
this.matrix[8] = t*x*z + s*y;
this.matrix[9] = t*y*z + s*x;
this.matrix[10] = c + t*z2;
return this;
}
矩阵存储在主要列中。