void GLCpuPosInstancedArraysBench::setupSingleVbo(const GrGLInterface* gl,
const SkMatrix* viewMatrices) {
// Constants for our various shader programs
Vertex vertices[kVerticesPerTri * kNumTri];
for (uint32_t i = 0; i < kNumTri; i++) {
Vertex* v = &vertices[i * kVerticesPerTri];
v[0].fPositions.set(-1.0f, -1.0f);
v[1].fPositions.set( 1.0f, -1.0f);
v[2].fPositions.set( 1.0f, 1.0f);
SkPoint* position = reinterpret_cast<SkPoint*>(v);
viewMatrices[i].mapPointsWithStride(position, sizeof(Vertex), kVerticesPerTri);
// set colors
float color = i == kNumTri - 1 ? 1.0f : 0.0f;
for (uint32_t j = 0; j < kVerticesPerTri; j++) {
uint32_t offset = 0;
v->fColors[offset++] = color; v->fColors[offset++] = 0.0f; v->fColors[offset++] = 0.0f;
v++;
}
}
GrGLuint vbo;
// setup VBO
GR_GL_CALL(gl, GenBuffers(1, &vbo));
GR_GL_CALL(gl, BindBuffer(GR_GL_ARRAY_BUFFER, vbo));
GR_GL_CALL(gl, EnableVertexAttribArray(0));
GR_GL_CALL(gl, EnableVertexAttribArray(1));
GR_GL_CALL(gl, VertexAttribPointer(0, 2, GR_GL_FLOAT, GR_GL_FALSE, sizeof(Vertex),
(GrGLvoid*)0));
GR_GL_CALL(gl, VertexAttribPointer(1, 3, GR_GL_FLOAT, GR_GL_FALSE, sizeof(Vertex),
(GrGLvoid*)(sizeof(SkPoint))));
GR_GL_CALL(gl, BufferData(GR_GL_ARRAY_BUFFER, sizeof(vertices), vertices, GR_GL_STATIC_DRAW));
fBuffers.push_back(vbo);
}
GrGLBuffer::GrGLBuffer(GrGLGpu* gpu, size_t size, GrGpuBufferType intendedType,
GrAccessPattern accessPattern, const void* data)
: INHERITED(gpu, size, intendedType, accessPattern)
, fIntendedType(intendedType)
, fBufferID(0)
, fUsage(gr_to_gl_access_pattern(intendedType, accessPattern))
, fGLSizeInBytes(0)
, fHasAttachedToTexture(false) {
GL_CALL(GenBuffers(1, &fBufferID));
if (fBufferID) {
GrGLenum target = gpu->bindBuffer(fIntendedType, this);
CLEAR_ERROR_BEFORE_ALLOC(gpu->glInterface());
// make sure driver can allocate memory for this buffer
GL_ALLOC_CALL(gpu->glInterface(), BufferData(target,
(GrGLsizeiptr) size,
data,
fUsage));
if (CHECK_ALLOC_ERROR(gpu->glInterface()) != GR_GL_NO_ERROR) {
GL_CALL(DeleteBuffers(1, &fBufferID));
fBufferID = 0;
} else {
fGLSizeInBytes = size;
}
}
VALIDATE();
this->registerWithCache(SkBudgeted::kYes);
if (!fBufferID) {
this->resourcePriv().removeScratchKey();
}
}
static uint32_t setup_quad_index_buffer(const GrGLInterface* gl) {
static const int kMaxQuads = 1;//1 << 12; // max possible: (1 << 14) - 1;
GR_STATIC_ASSERT(4 * kMaxQuads <= 65535);
static const uint16_t kPattern[] = { 0, 1, 2, 0, 2, 3 };
static const int kPatternSize = 6;
static const int kVertCount = 4;
static const int kIndicesCount = kPatternSize * kMaxQuads;
int size = kPatternSize * kMaxQuads * sizeof(uint16_t);
uint16_t* data = SkNEW_ARRAY(uint16_t, kMaxQuads * kPatternSize);
for (int i = 0; i < kMaxQuads; ++i) {
int baseIdx = i * kPatternSize;
uint16_t baseVert = (uint16_t)(i * kVertCount);
for (int j = 0; j < kPatternSize; ++j) {
data[baseIdx+j] = baseVert + kPattern[j];
}
}
GrGLuint quadIBO;
GR_GL_CALL(gl, GenBuffers(1, &quadIBO));
GR_GL_CALL(gl, BindBuffer(GR_GL_ELEMENT_ARRAY_BUFFER, quadIBO));
GR_GL_CALL(gl, BufferData(GR_GL_ELEMENT_ARRAY_BUFFER, size, data, GR_GL_STATIC_DRAW));
SkDELETE_ARRAY(data);
return kIndicesCount;
}
void GLCpuPosInstancedArraysBench::setupInstanceVbo(const GrGLInterface* gl,
const SkMatrix* viewMatrices) {
// We draw all of the instances at a single place because we aren't allowed to have per vertex
// per instance attributes
SkPoint positions[kVerticesPerTri];
positions[0].set(-1.0f, -1.0f);
positions[1].set( 1.0f, -1.0f);
positions[2].set( 1.0f, 1.0f);
viewMatrices[0].mapPointsWithStride(positions, sizeof(SkPoint), kVerticesPerTri);
// setup colors so we can detect we are actually drawing instances(the last triangle will be
// a different color)
GrGLfloat colors[kVerticesPerTri * kNumTri];
for (uint32_t i = 0; i < kNumTri; i++) {
// set colors
uint32_t offset = i * kVerticesPerTri;
float color = i == kNumTri - 1 ? 1.0f : 0.0f;
colors[offset++] = color; colors[offset++] = 0.0f; colors[offset++] = 0.0f;
}
GrGLuint posVBO;
// setup position VBO
GR_GL_CALL(gl, GenBuffers(1, &posVBO));
GR_GL_CALL(gl, BindBuffer(GR_GL_ARRAY_BUFFER, posVBO));
GR_GL_CALL(gl, BufferData(GR_GL_ARRAY_BUFFER, sizeof(positions), positions, GR_GL_STATIC_DRAW));
GR_GL_CALL(gl, EnableVertexAttribArray(0));
GR_GL_CALL(gl, VertexAttribPointer(0, 2, GR_GL_FLOAT, GR_GL_FALSE, 2 * sizeof(GrGLfloat),
(GrGLvoid*)0));
// setup color VBO
GrGLuint instanceVBO;
GR_GL_CALL(gl, GenBuffers(1, &instanceVBO));
GR_GL_CALL(gl, BindBuffer(GR_GL_ARRAY_BUFFER, instanceVBO));
GR_GL_CALL(gl, BufferData(GR_GL_ARRAY_BUFFER, sizeof(colors), colors, GR_GL_STATIC_DRAW));
GR_GL_CALL(gl, EnableVertexAttribArray(1));
GR_GL_CALL(gl, VertexAttribPointer(1, 3, GR_GL_FLOAT, GR_GL_FALSE, 3 * sizeof(GrGLfloat),
(GrGLvoid*)0));
GR_GL_CALL(gl, VertexAttribDivisor(1, 1));
fBuffers.push_back(posVBO);
fBuffers.push_back(instanceVBO);
}
void GLCpuPosInstancedArraysBench::setupDoubleVbo(const GrGLInterface* gl,
const SkMatrix* viewMatrices) {
// Constants for our various shader programs
SkPoint positions[kVerticesPerTri * kNumTri];
GrGLfloat colors[kVerticesPerTri * kNumTri * 3];
for (uint32_t i = 0; i < kNumTri; i++) {
SkPoint* position = &positions[i * kVerticesPerTri];
position[0].set(-1.0f, -1.0f);
position[1].set( 1.0f, -1.0f);
position[2].set( 1.0f, 1.0f);
viewMatrices[i].mapPointsWithStride(position, sizeof(SkPoint), kVerticesPerTri);
// set colors
float color = i == kNumTri - 1 ? 1.0f : 0.0f;
uint32_t offset = i * kVerticesPerTri * 3;
for (uint32_t j = 0; j < kVerticesPerTri; j++) {
colors[offset++] = color; colors[offset++] = 0.0f; colors[offset++] = 0.0f;
}
}
GrGLuint posVBO, colorVBO;
// setup position VBO
GR_GL_CALL(gl, GenBuffers(1, &posVBO));
GR_GL_CALL(gl, BindBuffer(GR_GL_ARRAY_BUFFER, posVBO));
GR_GL_CALL(gl, EnableVertexAttribArray(0));
GR_GL_CALL(gl, VertexAttribPointer(0, 2, GR_GL_FLOAT, GR_GL_FALSE, 2 * sizeof(GrGLfloat),
(GrGLvoid*)0));
GR_GL_CALL(gl, BufferData(GR_GL_ARRAY_BUFFER, sizeof(positions), positions, GR_GL_STATIC_DRAW));
// setup color VBO
GR_GL_CALL(gl, GenBuffers(1, &colorVBO));
GR_GL_CALL(gl, BindBuffer(GR_GL_ARRAY_BUFFER, colorVBO));
GR_GL_CALL(gl, EnableVertexAttribArray(1));
GR_GL_CALL(gl, VertexAttribPointer(1, 3, GR_GL_FLOAT, GR_GL_FALSE, 3 * sizeof(GrGLfloat),
(GrGLvoid*)0));
GR_GL_CALL(gl, BufferData(GR_GL_ARRAY_BUFFER, sizeof(colors), colors, GR_GL_STATIC_DRAW));
fBuffers.push_back(posVBO);
fBuffers.push_back(colorVBO);
}
void GL3CharacterRenderer::buildHead() {
GL(GenVertexArrays(1, &headVao));
GL(GenBuffers(1, &headVbo));
GL(BindVertexArray(headVao));
GL(BindBuffer(GL_ARRAY_BUFFER, headVbo));
GL(VertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 40, 0));
GL(VertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 40, (void *) 12));
GL(VertexAttribPointer(2, 4, GL_FLOAT, GL_FALSE, 40, (void *) 24));
GL(EnableVertexAttribArray(0));
GL(EnableVertexAttribArray(1));
GL(EnableVertexAttribArray(2));
GL(BindVertexArray(0));
VertexData vertexData[36];
int vertexIndices[6] = {0, 1, 2, 0, 2, 3};
int index = 0;
for (int d = 0; d < 6; d++) {
vec3f normal(0.0);
normal[d % 3] = DIRS[d][d % 3];
vec3f vertices[4];
for (int i = 0; i < 4; i++) {
vertices[i] = vec3f(
(DIR_QUAD_CORNER_CYCLES_3D[d][i][0] - 0.5f) * HEAD_SIZE[0],
(DIR_QUAD_CORNER_CYCLES_3D[d][i][1] - 0.5f) * HEAD_SIZE[1],
(DIR_QUAD_CORNER_CYCLES_3D[d][i][2] - 0.5f) * HEAD_SIZE[2] + HEAD_Z_OFFSET
) * (1.0f / RESOLUTION);
}
for (int j = 0; j < 6; j++) {
vertexData[index].xyz[0] = vertices[vertexIndices[j]][0];
vertexData[index].xyz[1] = vertices[vertexIndices[j]][1];
vertexData[index].xyz[2] = vertices[vertexIndices[j]][2];
vertexData[index].nxyz[0] = normal[0];
vertexData[index].nxyz[1] = normal[1];
vertexData[index].nxyz[2] = normal[2];
vertexData[index].rgba[0] = CHARACTER_COLOR[0];
vertexData[index].rgba[1] = CHARACTER_COLOR[1];
vertexData[index].rgba[2] = CHARACTER_COLOR[2];
vertexData[index].rgba[3] = 1.0f;
index++;
}
}
GL(BufferData(GL_ARRAY_BUFFER, sizeof(vertexData), vertexData, GL_STATIC_DRAW));
GL(BindBuffer(GL_ARRAY_BUFFER, 0));
}
GrGLBuffer::GrGLBuffer(GrGLGpu* gpu, size_t size, GrBufferType intendedType,
GrAccessPattern accessPattern, bool cpuBacked, const void* data)
: INHERITED(gpu, size, intendedType, accessPattern, cpuBacked),
fCPUData(nullptr),
fIntendedType(intendedType),
fBufferID(0),
fSizeInBytes(size),
fUsage(gr_to_gl_access_pattern(intendedType, accessPattern)),
fGLSizeInBytes(0),
fHasAttachedToTexture(false) {
if (this->isCPUBacked()) {
// Core profile uses vertex array objects, which disallow client side arrays.
SkASSERT(!gpu->glCaps().isCoreProfile());
if (gpu->caps()->mustClearUploadedBufferData()) {
fCPUData = sk_calloc_throw(fSizeInBytes);
} else {
fCPUData = sk_malloc_flags(fSizeInBytes, SK_MALLOC_THROW);
}
if (data) {
memcpy(fCPUData, data, fSizeInBytes);
}
} else {
GL_CALL(GenBuffers(1, &fBufferID));
if (fBufferID) {
GrGLenum target = gpu->bindBuffer(fIntendedType, this);
CLEAR_ERROR_BEFORE_ALLOC(gpu->glInterface());
// make sure driver can allocate memory for this buffer
GL_ALLOC_CALL(gpu->glInterface(), BufferData(target,
(GrGLsizeiptr) fSizeInBytes,
data,
fUsage));
if (CHECK_ALLOC_ERROR(gpu->glInterface()) != GR_GL_NO_ERROR) {
GL_CALL(DeleteBuffers(1, &fBufferID));
fBufferID = 0;
} else {
fGLSizeInBytes = fSizeInBytes;
}
}
}
VALIDATE();
this->registerWithCache(SkBudgeted::kYes);
}
/*******************************************************************************
*
* Private functions.
*
******************************************************************************/
int
rb_ogl3_create_buffer
(struct rb_context* ctxt,
const struct rb_ogl3_buffer_desc* desc,
const void* init_data,
struct rb_buffer** out_buffer)
{
struct rb_buffer* buffer = NULL;
if(!ctxt
|| !desc
|| !out_buffer
|| (desc->target == RB_OGL3_NB_BUFFER_TARGETS)
|| (desc->usage == RB_USAGE_IMMUTABLE && init_data == NULL))
return -1;
buffer = MEM_ALLOC(ctxt->allocator, sizeof(struct rb_buffer));
if(!buffer)
return -1;
ref_init(&buffer->ref);
RB(context_ref_get(ctxt));
buffer->ctxt = ctxt;
buffer->target = rb_to_ogl3_buffer_target(desc->target);
buffer->usage = rb_to_ogl3_usage(desc->usage);
buffer->size = (GLsizei)desc->size;
buffer->binding = desc->target;
OGL(GenBuffers(1, &buffer->name));
OGL(BindBuffer(buffer->target, buffer->name));
OGL(BufferData(buffer->target, buffer->size, init_data, buffer->usage));
OGL(BindBuffer
(buffer->target,
ctxt->state_cache.buffer_binding[buffer->binding]));
*out_buffer = buffer;
return 0;
}
void GLVec4ScalarBench::setupSingleVbo(const GrGLInterface* gl, const SkMatrix* viewMatrices) {
// triangles drawn will alternate between the top-right half of the screen and the bottom-left
// half of the screen
Vertex vertices[kVerticesPerTri * kNumTriPerDraw];
for (uint32_t i = 0; i < kNumTriPerDraw; i++) {
Vertex* v = &vertices[i * kVerticesPerTri];
if (i % 2 == 0) {
v[0].fPositions.set(-1.0f, -1.0f);
v[1].fPositions.set( 1.0f, -1.0f);
v[2].fPositions.set( 1.0f, 1.0f);
} else {
v[0].fPositions.set(-1.0f, -1.0f);
v[1].fPositions.set( 1.0f, 1.0f);
v[2].fPositions.set( -1.0f, 1.0f);
}
SkPoint* position = reinterpret_cast<SkPoint*>(v);
viewMatrices[i].mapPointsWithStride(position, sizeof(Vertex), kVerticesPerTri);
GrGLfloat color[3] = {1.0f, 0.0f, 1.0f};
for (uint32_t j = 0; j < kVerticesPerTri; j++) {
v->fColors[0] = color[0];
v->fColors[1] = color[1];
v->fColors[2] = color[2];
v++;
}
}
GR_GL_CALL(gl, GenBuffers(1, &fVboId));
GR_GL_CALL(gl, BindBuffer(GR_GL_ARRAY_BUFFER, fVboId));
GR_GL_CALL(gl, EnableVertexAttribArray(0));
GR_GL_CALL(gl, EnableVertexAttribArray(1));
GR_GL_CALL(gl, VertexAttribPointer(0, 2, GR_GL_FLOAT, GR_GL_FALSE, sizeof(Vertex),
(GrGLvoid*)0));
GR_GL_CALL(gl, VertexAttribPointer(1, 3, GR_GL_FLOAT, GR_GL_FALSE, sizeof(Vertex),
(GrGLvoid*)(sizeof(SkPoint))));
GR_GL_CALL(gl, BufferData(GR_GL_ARRAY_BUFFER, sizeof(vertices), vertices, GR_GL_STATIC_DRAW));
}
void GLGpuPosInstancedArraysBench::setup(const GrGLInterface* gl) {
setup_framebuffer(gl, kScreenWidth, kScreenHeight);
// compile and use shaders
GrGLint shaderProgram = compile_shader(gl, gpu_vertex_shader, fragment_shader);
// translations
int index = 0;
GrGLfloat viewMatrices[fNumQuads * fSkMatrixNumCells];
setup_matrices(fNumQuads, [&index, &viewMatrices](const SkMatrix& m) {
GrGLGetMatrix<3>(&viewMatrices[index], m);
index += fSkMatrixNumCells;
});
// Constants for our various shader programs
GrGLfloat quad_vertices[] = {
// Positions // Colors
-1.0f, 1.0f, 1.0f, 0.0f, 0.0f,
1.0f, -1.0f, 0.0f, 1.0f, 0.0f,
-1.0f, -1.0f, 0.0f, 0.0f, 1.0f,
-1.0f, 1.0f, 1.0f, 0.0f, 0.0f,
1.0f, -1.0f, 0.0f, 1.0f, 0.0f,
1.0f, 1.0f, 0.0f, 1.0f, 1.0f
};
// update vertex data
GrGLuint quadVAO, quadVBO;
GR_GL_CALL(gl, GenVertexArrays(1, &quadVAO));
GR_GL_CALL(gl, GenBuffers(1, &quadVBO));
GR_GL_CALL(gl, BindVertexArray(quadVAO));
GR_GL_CALL(gl, BindBuffer(GR_GL_ARRAY_BUFFER, quadVBO));
GR_GL_CALL(gl, EnableVertexAttribArray(0));
GR_GL_CALL(gl, VertexAttribPointer(0, 2, GR_GL_FLOAT, GR_GL_FALSE, 5 * sizeof(GrGLfloat), (GrGLvoid*)0));
GR_GL_CALL(gl, EnableVertexAttribArray(1));
GR_GL_CALL(gl, VertexAttribPointer(1, 3, GR_GL_FLOAT, GR_GL_FALSE, 5 * sizeof(GrGLfloat), (GrGLvoid*)(2 * sizeof(GrGLfloat))));
GR_GL_CALL(gl, BufferData(GR_GL_ARRAY_BUFFER, sizeof(quad_vertices), quad_vertices, GR_GL_STATIC_DRAW));
// Also set instance data
GrGLuint instanceVBO;
GR_GL_CALL(gl, GenBuffers(1, &instanceVBO));
GR_GL_CALL(gl, BindBuffer(GR_GL_ARRAY_BUFFER, instanceVBO));
GR_GL_CALL(gl, BufferData(GR_GL_ARRAY_BUFFER, sizeof(GrGLfloat) * fSkMatrixNumCells * fNumQuads,
&viewMatrices[0], GR_GL_STATIC_DRAW));
GR_GL_CALL(gl, EnableVertexAttribArray(2));
GR_GL_CALL(gl, EnableVertexAttribArray(3));
GR_GL_CALL(gl, EnableVertexAttribArray(4));
GR_GL_CALL(gl, VertexAttribPointer(2, 3, GR_GL_FLOAT, GR_GL_FALSE, 9 * sizeof(GrGLfloat), (GrGLvoid*)0));
GR_GL_CALL(gl, VertexAttribPointer(3, 3, GR_GL_FLOAT, GR_GL_FALSE, 9 * sizeof(GrGLfloat), (GrGLvoid*)(3 * sizeof(GrGLfloat))));
GR_GL_CALL(gl, VertexAttribPointer(4, 3, GR_GL_FLOAT, GR_GL_FALSE, 9 * sizeof(GrGLfloat), (GrGLvoid*)(6 * sizeof(GrGLfloat))));
GR_GL_CALL(gl, VertexAttribDivisor(2, 1));
GR_GL_CALL(gl, VertexAttribDivisor(3, 1));
GR_GL_CALL(gl, VertexAttribDivisor(4, 1));
// draw
GR_GL_CALL(gl, ClearColor(0.03f, 0.03f, 0.03f, 1.0f));
GR_GL_CALL(gl, Clear(GR_GL_COLOR_BUFFER_BIT));
// set us up to draw
GR_GL_CALL(gl, UseProgram(shaderProgram));
GR_GL_CALL(gl, BindVertexArray(quadVAO));
}
GLuint GLInterfaceWrapper::CreateBuffer() const {
GLuint buffer = 0;
GenBuffers( 1, &buffer );
return buffer;
}
bool Animation::Mesh::InitFromScene(const aiScene* scene, const std::string& filename)
{
Clear();
GenBuffers();
m_meshes.resize(scene->mNumMeshes);
std::vector<unsigned int> indices;
std::vector<VertexInfo> vertices;
m_numVertices = 0;
m_numIndices = 0;
Assign(m_GlobalInverseTransform, scene->mRootNode->mTransformation);
m_GlobalInverseTransform = glm::inverse(m_GlobalInverseTransform);
// Count the number of vertices and indices
for (unsigned int i = 0; i < m_meshes.size(); i++)
{
m_meshes[i].materialIndex = scene->mMeshes[i]->mMaterialIndex;
m_meshes[i].numIndices = scene->mMeshes[i]->mNumFaces * 3;
m_meshes[i].baseVertex = m_numVertices;
m_meshes[i].baseIndex = m_numIndices;
m_numVertices += scene->mMeshes[i]->mNumVertices;
m_numIndices += m_meshes[i].numIndices;
}
// Reserve space in the vectors for the vertex attributes and indices
vertices.reserve(m_numVertices);
indices.reserve(m_numIndices);
InitNodeHierarchy(m_rootNode, scene->mRootNode);
// Initialize the meshes in the scene one by one
for (unsigned int i = 0; i < m_meshes.size(); i++)
{
const aiMesh* paiMesh = scene->mMeshes[i];
InitMesh(i, paiMesh, vertices, indices);
}
if (!InitMaterials(scene, filename))
return false;
// Populate the buffers with vertex attributes and the indices
glBindVertexArray(m_VAO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_EBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices[0]) * indices.size(), &indices[0], GL_STATIC_DRAW);
// Load data
glBindBuffer(GL_ARRAY_BUFFER, m_VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(VertexInfo) * vertices.size(), &vertices[0], GL_STATIC_DRAW);
glEnableVertexAttribArray(POSITION_LOCATION);
glVertexAttribPointer(POSITION_LOCATION, 3, GL_FLOAT, GL_FALSE, sizeof(VertexInfo),
(GLvoid*)0);
glEnableVertexAttribArray(TEX_COORD_LOCATION);
glVertexAttribPointer(TEX_COORD_LOCATION, 2, GL_FLOAT, GL_FALSE, sizeof(VertexInfo),
(GLvoid*)offsetof(VertexInfo, texCoords));
glEnableVertexAttribArray(NORMAL_LOCATION);
glVertexAttribPointer(NORMAL_LOCATION, 3, GL_FLOAT, GL_FALSE, sizeof(VertexInfo),
(GLvoid*)offsetof(VertexInfo, normal));
glEnableVertexAttribArray(BONE_ID_LOCATION);
glVertexAttribIPointer(BONE_ID_LOCATION, 4, GL_UNSIGNED_INT, sizeof(VertexInfo), // Cannot pass more than 4!!
(GLvoid*)offsetof(VertexInfo, boneData.IDs));
glEnableVertexAttribArray(BONE_WEIGHT_LOCATION);
glVertexAttribPointer(BONE_WEIGHT_LOCATION, 4, GL_FLOAT, GL_FALSE, sizeof(VertexInfo), // Cannot pass more than 4!!
(GLvoid*)offsetof(VertexInfo, boneData.weights));
glBindVertexArray(0); // Make sure the VAO is not changed from the outside
return glGetError() == GL_NO_ERROR;
}