我正在尝试为Android编写一个Flutter插件，允许我使用Texture直接写入像素，因此我需要提供SurfaceTexture，并且我希望能够使用单个纹理四边形为其绘制任意像素数据。现在，为了调试，我只是试图在品红色背景上绘制一个青色三角形，以验证我的顶点是否被正确绘制，但看起来它们不是。glClear调用正在做我所期望的事情，因为显示的是品红色背景，而不是后面的黑色，我可以通过更改传递给glClearColor的内容来更改该颜色，所以在某种程度上，纹理正在渲染，但我看不到调用glDrawArrays有任何效果的证据。包含我与OpenGL ES的所有接口的代码在下面的文件中，drawTextureToCurrentSurface方法是调用glClear和glDrawArrays的地方：
class EglContext {
companion object {
// Pass through position and UV values
val vertexSource = """
#version 300 es
precision mediump float;
/*layout(location = 0)*/ in vec2 position;
/*layout(location = 1)*/ in vec2 uv;
out vec2 uvOut;
void main() {
gl_Position = vec4(position, -0.5, 1.0);
uvOut = uv;
}
""".trimIndent()
// Eventually get the texture value, for now, just make it cyan so I can see it
val fragmentSource = """
#version 300 es
precision mediump float;
in vec2 uvOut;
out vec4 fragColor;
uniform sampler2D tex;
void main() {
vec4 texel = texture(tex, uvOut);
// Effectively ignore the texel without optimizing it out
fragColor = texel * 0.0001 + vec4(0.0, 1.0, 1.0, 1.0);
}
""".trimIndent()
var glThread: HandlerThread? = null
var glHandler: Handler? = null
}
private var display = EGL14.EGL_NO_DISPLAY
private var context = EGL14.EGL_NO_CONTEXT
private var config: EGLConfig? = null
private var vertexBuffer: FloatBuffer
private var uvBuffer: FloatBuffer
//private var indexBuffer: IntBuffer
private var defaultProgram: Int = -1
private var uniformTextureLocation: Int = -1
private var vertexLocation: Int = -1
private var uvLocation: Int = -1
var initialized = false
private fun checkGlError(msg: String) {
val errCodeEgl = EGL14.eglGetError()
val errCodeGl = GLES30.glGetError()
if (errCodeEgl != EGL14.EGL_SUCCESS || errCodeGl != GLES30.GL_NO_ERROR) {
throw RuntimeException(
"$msg - $errCodeEgl(${GLU.gluErrorString(errCodeEgl)}) : $errCodeGl(${
GLU.gluErrorString(
errCodeGl
)
})"
)
}
}
init {
// Flat square
// Am I allocating and writing to these correctly?
val vertices = floatArrayOf(-1f, -1f, 1f, -1f, -1f, 1f, 1f, 1f)
vertexBuffer = ByteBuffer.allocateDirect(vertices.size * 4).asFloatBuffer().also {
it.put(vertices)
it.position(0)
}
val uv = floatArrayOf(0f, 0f, 1f, 0f, 0f, 1f, 1f, 1f)
uvBuffer = ByteBuffer.allocateDirect(uv.size * 4).asFloatBuffer().also {
it.put(uv)
it.position(0)
}
// Not being used until I can figure out what's currently not working
/*val indices = intArrayOf(0, 1, 2, 2, 1, 3)
indexBuffer = ByteBuffer.allocateDirect(indices.size * 4).asIntBuffer().also {
it.position(0)
it.put(indices)
it.position(0)
}*/
if (glThread == null) {
glThread = HandlerThread("flutterSoftwareRendererPlugin")
glThread!!.start()
glHandler = Handler(glThread!!.looper)
}
}
// Run OpenGL code on a separate thread to keep the context available
private fun doOnGlThread(blocking: Boolean = true, task: () -> Unit) {
val semaphore: Semaphore? = if (blocking) Semaphore(0) else null
glHandler!!.post {
task.invoke()
semaphore?.release()
}
semaphore?.acquire()
}
fun setup() {
doOnGlThread {
Log.d("Native", "Setting up EglContext")
display = EGL14.eglGetDisplay(EGL14.EGL_DEFAULT_DISPLAY)
if (display == EGL14.EGL_NO_DISPLAY) {
Log.e("Native", "No display")
checkGlError("Failed to get display")
}
val versionBuffer = IntArray(2)
if (!EGL14.eglInitialize(display, versionBuffer, 0, versionBuffer, 1)) {
Log.e("Native", "Did not init")
checkGlError("Failed to initialize")
}
val configs = arrayOfNulls<EGLConfig>(1)
val configNumBuffer = IntArray(1)
var attrBuffer = intArrayOf(
EGL14.EGL_RENDERABLE_TYPE, EGL14.EGL_OPENGL_ES2_BIT,
EGL14.EGL_RED_SIZE, 8,
EGL14.EGL_GREEN_SIZE, 8,
EGL14.EGL_BLUE_SIZE, 8,
EGL14.EGL_ALPHA_SIZE, 8,
EGL14.EGL_DEPTH_SIZE, 16,
//EGL14.EGL_STENCIL_SIZE, 8,
//EGL14.EGL_SAMPLE_BUFFERS, 1,
//EGL14.EGL_SAMPLES, 4,
EGL14.EGL_NONE
)
if (!EGL14.eglChooseConfig(
display,
attrBuffer,
0,
configs,
0,
configs.size,
configNumBuffer,
0
)
) {
Log.e("Native", "No config")
checkGlError("Failed to choose a config")
}
if (configNumBuffer[0] == 0) {
Log.e("Native", "No config")
checkGlError("Got zero configs")
}
Log.d("Native", "Got Config x${configNumBuffer[0]}: ${configs[0]}")
config = configs[0]
attrBuffer = intArrayOf(
EGL14.EGL_CONTEXT_CLIENT_VERSION, 2, EGL14.EGL_NONE
)
context = EGL14.eglCreateContext(display, config, EGL14.EGL_NO_CONTEXT, attrBuffer, 0)
if (context == EGL14.EGL_NO_CONTEXT) {
Log.e("Native", "Failed to get any context")
checkGlError("Failed to get context")
}
Log.d("Native", "Context = $contextn 'Current' = ${EGL14.eglGetCurrentContext()}")
initialized = true
}
}
// Called by my plugin to get a surface to register for Texture widget
fun buildSurfaceTextureWindow(surfaceTexture: SurfaceTexture): EGLSurface {
var _surface: EGLSurface? = null
doOnGlThread {
val attribBuffer = intArrayOf(EGL14.EGL_NONE)
val surface =
EGL14.eglCreateWindowSurface(display, config, surfaceTexture, attribBuffer, 0)
if (surface == EGL14.EGL_NO_SURFACE) {
checkGlError("Obtained no surface")
}
EGL14.eglMakeCurrent(display, surface, surface, context)
Log.d("Native", "New current context = ${EGL14.eglGetCurrentContext()}")
if (defaultProgram == -1) {
defaultProgram = makeProgram(
mapOf(
GLES30.GL_VERTEX_SHADER to vertexSource,
GLES30.GL_FRAGMENT_SHADER to fragmentSource
)
)
uniformTextureLocation = GLES30.glGetUniformLocation(defaultProgram, "tex")
vertexLocation = GLES30.glGetAttribLocation(defaultProgram, "position")
uvLocation = GLES30.glGetAttribLocation(defaultProgram, "uv")
Log.d("Native", "Attrib locations $vertexLocation, $uvLocation")
checkGlError("Getting uniform")
}
_surface = surface
}
return _surface!!
}
fun makeCurrent(eglSurface: EGLSurface, width: Int, height: Int) {
doOnGlThread {
GLES30.glViewport(0, 0, width, height)
if (!EGL14.eglMakeCurrent(display, eglSurface, eglSurface, context)) {
checkGlError("Failed to make surface current")
}
}
}
fun makeTexture(width: Int, height: Int): Int {
var _texture: Int? = null
doOnGlThread {
val intArr = IntArray(1)
GLES30.glGenTextures(1, intArr, 0)
checkGlError("Generate texture")
Log.d("Native", "${EGL14.eglGetCurrentContext()} ?= ${EGL14.EGL_NO_CONTEXT}")
val texture = intArr[0]
Log.d("Native", "Texture = $texture")
GLES30.glBindTexture(GLES30.GL_TEXTURE_2D, texture)
checkGlError("Bind texture")
val buffer = ByteBuffer.allocateDirect(width * height * 4)
GLES30.glTexImage2D(
GLES30.GL_TEXTURE_2D,
0,
GLES30.GL_RGBA,
width,
height,
0,
GLES30.GL_RGBA,
GLES30.GL_UNSIGNED_BYTE,
buffer
)
checkGlError("Create texture buffer")
_texture = texture
}
return _texture!!
}
private fun compileShader(source: String, shaderType: Int): Int {
val currentContext = EGL14.eglGetCurrentContext()
val noContext = EGL14.EGL_NO_CONTEXT
val shaderId = GLES30.glCreateShader(shaderType)
Log.d("Native", "Created $shaderIdnContext $currentContext vs $noContext")
checkGlError("Create shader")
if (shaderId == 0) {
Log.e("Native", "Could not create shader for some reason")
checkGlError("Could not create shader")
}
GLES30.glShaderSource(shaderId, source)
checkGlError("Setting shader source")
GLES30.glCompileShader(shaderId)
val statusBuffer = IntArray(1)
GLES30.glGetShaderiv(shaderId, GLES30.GL_COMPILE_STATUS, statusBuffer, 0)
val shaderLog = GLES30.glGetShaderInfoLog(shaderId)
Log.d("Native", "Compiling shader #$shaderId : $shaderLog")
if (statusBuffer[0] == 0) {
GLES30.glDeleteShader(shaderId)
checkGlError("Failed to compile shader $shaderId")
}
return shaderId
}
private fun makeProgram(sources: Map<Int, String>): Int {
val currentContext = EGL14.eglGetCurrentContext()
val noContext = EGL14.EGL_NO_CONTEXT
val program = GLES30.glCreateProgram()
Log.d("Native", "Created $programnContext $currentContext vs $noContext")
checkGlError("Create program")
sources.forEach {
val shader = compileShader(it.value, it.key)
GLES30.glAttachShader(program, shader)
}
val linkBuffer = IntArray(1)
GLES30.glLinkProgram(program)
GLES30.glGetProgramiv(program, GLES30.GL_LINK_STATUS, linkBuffer, 0)
if (linkBuffer[0] == 0) {
GLES30.glDeleteProgram(program)
checkGlError("Failed to link program $program")
}
return program
}
// Called to actually draw to the surface. When fully implemented it should draw whatever is
// on the associated texture, but for now, to debug, I just want to verify I can draw vertices,
// but it seems I cannot?
fun drawTextureToCurrentSurface(texture: Int, surface: EGLSurface) {
doOnGlThread {
// Verify I have a context
val currentContext = EGL14.eglGetCurrentContext()
val noContext = EGL14.EGL_NO_CONTEXT
Log.d("Native", "Drawing, Context = $currentContext vs $noContext")
checkGlError("Just checking first")
GLES30.glClearColor(1f, 0f, 1f, 1f)
GLES30.glClearDepthf(1f)
GLES30.glDisable(GLES30.GL_DEPTH_TEST)
GLES30.glClear(GLES30.GL_COLOR_BUFFER_BIT or GLES30.GL_DEPTH_BUFFER_BIT)
checkGlError("Clearing")
GLES30.glUseProgram(defaultProgram)
checkGlError("Use program")
GLES30.glActiveTexture(GLES30.GL_TEXTURE0)
checkGlError("Activate texture 0")
GLES30.glBindTexture(GLES30.GL_TEXTURE_2D, texture)
checkGlError("Bind texture $texture")
GLES30.glUniform1i(uniformTextureLocation, 0)
checkGlError("Set uniform")
GLES30.glEnableVertexAttribArray(vertexLocation)
vertexBuffer.position(0)
GLES30.glVertexAttribPointer(vertexLocation, 2, GLES30.GL_FLOAT, false, 0, vertexBuffer)
Log.d("Native", "Bound vertices (shader=$defaultProgram)")
checkGlError("Attribute 0")
GLES30.glEnableVertexAttribArray(uvLocation)
uvBuffer.position(0)
GLES30.glVertexAttribPointer(uvLocation, 2, GLES30.GL_FLOAT, false, 0, uvBuffer)
checkGlError("Attribute 1")
//indexBuffer.position(0)
//GLES30.glDrawElements(GLES30.GL_TRIANGLES, 4, GLES30.GL_UNSIGNED_INT, indexBuffer)
// I would expect to get a triangle of different color than the background
GLES30.glDrawArrays(GLES30.GL_TRIANGLE_STRIP, 0, 3)
GLES30.glFinish()
checkGlError("Finished GL")
EGL14.eglSwapBuffers(display, surface)
checkGlError("Swapped buffers")
}
}
...currently unused other methods
}
上述代码的一般流程是init块在初始化上下文时执行，上下文只有一个。注册插件时调用setup，初始化FlutterTexture的SurfaceTexture时调用buildSurfaceTextureWindow。第一次调用时，它会编译着色器。当插件想要渲染纹理时，它会调用makeCurrent，然后调用drawTextureToCurrentSurface，这是品红色背景变得可见但没有任何青色三角形的地方。对GL函数的调用是使用doOnGlThread在单独的线程中完成的。
如果你需要查看所有的代码，包括完整的插件实现和使用它的示例应用程序，我在Github上有它，但据我所知，上面的代码应该是唯一相关的区域，不会看到任何以片段着色器的有效硬编码颜色渲染的几何体。
tl；dr我来自glClear的背景色显示在屏幕上，但我调用glDrawArrays(青色三角形(的预期结果没有，我正在努力理解原因。
显然我需要在缓冲区上调用.order(ByteOrder.nativeOrder())。如果没有这一点，顶点阵列数据将无法正确设置。此外，我还需要为GL_TEXTURE_MAG/MIN_FILTER和GL_TEXTURE_WRAP_S/T设置glTexParameteri(GL_TEXTURE_2D, ...)。没有它，所有纹理都是黑色