问题描述
我正在尝试在 Android 的 OPENGL 中创建一个球体。 目前,我只是在绘制赤道,但是当我添加多个顶点 (stp=10) 时,应用程序崩溃并出现此错误:
A/libc: Fatal signal 11 (SIGSEGV),code 2,fault addr 0x751b5360 in tid 2588 (GLThread 3395)
但是当我减少顶点数 (stp=20) 时,它会显示赤道:
这是我的代码:
import COORDS_PER_VERTEX
import android.opengl.GLES20
import android.opengl.GLES20.GL_FLOAT
import java.nio.ByteBuffer
import java.nio.ByteOrder
import java.nio.FloatBuffer
import kotlin.math.*
class SkyGrid {
private var vertexCount: Int = 0
private var vertexBuffer: FloatBuffer
val stp=20
private val vertexshadercode =
// This matrix member variable provides a hook to manipulate
// the coordinates of the objects that use this vertex shader
"uniform mat4 uMVPMatrix;" +
"attribute vec4 vPosition;" +
"void main() {" +
// the matrix must be included as a modifier of gl_Position
// Note that the uMVPMatrix factor *must be first* in order
// for the matrix multiplication product to be correct.
" gl_Position = uMVPMatrix * vPosition;" +
"}"
// Use to access and set the view transformation
private var vPMatrixHandle: Int = 0
private val fragmentshadercode =
"precision mediump float;" +
"uniform vec4 vColor;" +
"void main() {" +
" gl_FragColor = vColor;" +
"}"
fun loadShader(type: Int,shadercode: String): Int {
// create a vertex shader type (GLES20.GL_VERTEX_SHADER)
// or a fragment shader type (GLES20.GL_FRAGMENT_SHADER)
return GLES20.glCreateShader(type).also { shader ->
// add the source code to the shader and compile it
GLES20.glShaderSource(shader,shadercode)
GLES20.glCompileShader(shader)
}
}
private var mProgram: Int
init {
val vertexShader: Int = loadShader(GLES20.GL_VERTEX_SHADER,vertexshadercode)
val fragmentShader: Int = loadShader(GLES20.GL_FRAGMENT_SHADER,fragmentshadercode)
// create empty OpenGL ES Program
mProgram = GLES20.glCreateProgram().also {
// add the vertex shader to program
GLES20.glAttachShader(it,vertexShader)
// add the fragment shader to program
GLES20.glAttachShader(it,fragmentShader)
// creates OpenGL ES program executables
GLES20.glLinkProgram(it)
}
var triangleCoords: MutableList<Float> = mutablelistof();
for (a in 0..360 step stp)
{
val r=0.5f
val alpha=Math.PI* a/180.0
val x=r*cos(alpha).toFloat()
val y=r*sin(alpha).toFloat()
var p1=arrayOf(x,y,0.0f)
val alpha2=Math.PI* (a+stp)/180.0
val x2=r*cos(alpha2).toFloat()
val y2=r*sin(alpha2).toFloat()
var p2=arrayOf(x2,y2,0.0f)
triangleCoords.addAll(p1)
triangleCoords.addAll(p2)
}
vertexCount = triangleCoords.size
vertexBuffer =
// (number of coordinate values * 4 bytes per float)
ByteBuffer.allocateDirect(triangleCoords.size * 4).run {
// use the device hardware's native byte order
order(ByteOrder.nativeOrder())
// create a floating point buffer from the ByteBuffer
asFloatBuffer().apply {
// add the coordinates to the FloatBuffer
put(triangleCoords.toFloatArray())
// set the buffer to read the first coordinate
position(0)
}
}
}
// Set color with red,green,blue and alpha (opacity) values
val color = floatArrayOf(0.13671875f,0.76953125f,0.22265625f,1.0f)
private var positionHandle: Int = 0
private var mColorHandle: Int = 0
private val vertexStride: Int = COORDS_PER_VERTEX * 4 // 4 bytes per vertex
fun draw(mvpMatrix: FloatArray) {
// Add program to OpenGL ES environment
GLES20.gluseProgram(mProgram)
// get handle to shape's transformation matrix
vPMatrixHandle = GLES20.glGetUniformlocation(mProgram,"uMVPMatrix")
// Pass the projection and view transformation to the shader
GLES20.gluniformMatrix4fv(vPMatrixHandle,1,false,mvpMatrix,0)
// get handle to vertex shader's vPosition member
positionHandle = GLES20.glGetAttribLocation(mProgram,"vPosition").also {
// Enable a handle to the triangle vertices
GLES20.glEnabLevertexAttribArray(it)
// Prepare the triangle coordinate data
GLES20.glVertexAttribPointer(
it,COORDS_PER_VERTEX,GLES20.GL_FLOAT,vertexStride,vertexBuffer
)
// get handle to fragment shader's vColor member
mColorHandle = GLES20.glGetUniformlocation(mProgram,"vColor").also { colorHandle ->
// Set color for drawing the triangle
GLES20.gluniform4fv(colorHandle,color,0)
}
// Draw the triangle
GLES20.glDrawArrays(GLES20.GL_LInes,vertexCount)
// disable vertex array
GLES20.gldisabLevertexAttribArray(it)
}
}
}
解决方法
glDrawArrays 的第三个扩充应该是顶点数(不是 #vertex-components)。适当计算参数。
//vertexCount = triangleCoords.size
vertexCount = triangleCoords.size / COORDS_PER_VERTEX
:
GLES20.glDrawArrays(GLES20.GL_LINES,vertexCount)