我正在尝试使用 C# 在 Android Xamarin 中绘制三角形。三角形是一个带有draw方法的类。在这个绘制方法中,有一个 openGL20 方法用于为我们刚刚创建的三角形对象着色。每当执行在 draw
方法到达此颜色对象方法,抛出此异常Java.Lang.IllegalArgumentException Message=length - offset < count*4 < needed
。
我真的不明白这个错误意味着什么,但这是迄今为止正在使用的代码
public class MyGLRenderer : Java.Lang.Object, GLSurfaceView.IRenderer
{
//Renderer method to draw the triangle object
public void OnDrawFrame(IGL10 gl)
{
GLES20.GlClear(GLES20.GlColorBufferBit);
Triangle triangle = new Triangle();
triangle.draw();
}
//Method to set the view and the height of the painting window
public void OnSurfaceChanged(IGL10 gl, int width, int height)
{
GLES20.GlViewport(0, 0, width, height);
}
public void OnSurfaceCreated(IGL10 gl, Javax.Microedition.Khronos.Egl.EGLConfig config)
{
//Set the background frame color
GLES20.GlClearColor(0.0f, 0.0f, 1.0f, 0.0f);
GLES20.GlDrawArrays(GLES20.GlColorBufferBit, 2, 10);
}
}
下面的代码定义了 Triangle 类和抛出注释异常的 OPENGL20 颜色方法
public class Triangle
{
private FloatBuffer vertexBuffer;
//Number of co-ordinates per vertex in this context
private static readonly int Coords_per_vert = 3;
private static float[] triangleCoords = new float[] {
0.0f,0.622008459f,0.0f, //top
-0.5f,-0.311004243f,0f , //bottom left
0.5f, -0.311004243f,0.0f //bottom right
};
//Set color with red, green, blue and alpha values
private float[] color = new float[] { 0.63671875f, 0.76953125f, 0.22265625f };
private readonly int mProgram;
public Triangle()
{
//Initialize vertex byte buffer for shape co-ordinates
ByteBuffer bb = ByteBuffer.AllocateDirect(triangleCoords.Length * 4);
//Use the device native byte order
bb.Order(ByteOrder.NativeOrder());
FloatBuffer myfloat = bb.AsFloatBuffer();
//Create floating point buffer from ByteBuffer
vertexBuffer = bb.AsFloatBuffer();
vertexBuffer.Put(triangleCoords);
vertexBuffer.Position(0);
int vertexShader = MyGLRenderer.loadShader(GLES20.GlVertexShader, vertexShaderCode);
int fragmentShader = MyGLRenderer.loadShader(GLES20.GlFragmentShader, fragmentShaderCode);
//Create empty opengles program
mProgram = GLES20.GlCreateProgram();
//Add vertex shader to program
GLES20.GlAttachShader(mProgram, vertexShader);
//Add Fragment to shader
GLES20.GlAttachShader(mProgram, fragmentShader);
//Create openGL program executables
GLES20.GlLinkProgram(mProgram);
}
private readonly string vertexShaderCode = "attribute vec4 vPosition;" +
"void main(){" +
" gl_Position=vPosition;" +
"}";
private readonly string fragmentShaderCode = "precision mediump float;" +
"uniform vec4 vColor;" +
"void main(){" +
"gl_FragColor=vColor;" +
"}";
private int positionHandle, colorHandle;
private readonly int vertexCount = triangleCoords.Length / Coords_per_vert;
private readonly int vertexStride = Coords_per_vert * 4;
//Create a method for drawing the triangle
public void draw()
{
//Add Program to open GLES Environment
GLES20.GlUseProgram(mProgram);
//Get handle to vertex shader's vPosition member
positionHandle = GLES20.GlGetAttribLocation(mProgram, "vPosition");
//Enable a handle to the triangle's vertices
GLES20.GlEnableVertexAttribArray(positionHandle);
//Prepare the triangle co ordinate data
GLES20.GlVertexAttribPointer(positionHandle, Coords_per_vert, GLES20.GlFloat, false, vertexStride, vertexBuffer);
//Get handle to fragment shader's vColor Member
colorHandle = GLES20.GlGetUniformLocation(mProgram, "vColor");
//Set color for drawing the triangle
GLES20.GlUniform4fv(colorHandle, 1, color, 3);
//Draw the triangle, this method causes an exception
GLES20.GlDrawArrays(GLES20.GlTriangles, 0, vertexCount);
//Disable vertex array
GLES20.GlDisableVertexAttribArray(positionHandle);
}
}
请帮我成功地为三角形对象着色,我做错了什么
最佳答案
您正在使用 3 大小的 float 组作为 vec4 制服。 像这样将 alpha 数组添加到颜色数组中 替换
private float[] color = new float[] { 0.63671875f, 0.76953125f, 0.22265625f };
与
private float[] color = new float[] { 0.63671875f, 0.76953125f, 0.22265625f,1.0f};
第二个数组的最后一个成员表示所绘制颜色的 Alpha 或不透明度
关于c# - OPENGLES 20 `` `GlUniform4fv ``` 为对象着色的方法在 C# Android 中抛出异常,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/66427661/