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I am creating a color picker OpenGL application for images with ImGUI. I have managed to load an image by loading the image into a glTexImage2D and using ImGUI::Image().
Now I would like to implement a method, which can determine the color of the pixel in case of a left mouse click.
Here is the method I loading the texture, then assigning it to a framebuffer:
bool LoadTextureFromFile(const char *filename, GLuint *out_texture, int *out_width, int *out_height,ImVec2 mousePosition ) {
// Reading the image into a GL_TEXTURE_2D
int image_width = 0;
int image_height = 0;
unsigned char *image_data = stbi_load(filename, &image_width, &image_height, NULL, 4);
if (image_data == NULL)
return false;
GLuint image_texture;
glGenTextures(1, &image_texture);
glBindTexture(GL_TEXTURE_2D, image_texture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, image_width, image_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, image_data);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
stbi_image_free(image_data);
glBindTexture(GL_TEXTURE_2D, 0);
*out_texture = image_texture;
*out_width = image_width;
*out_height = image_height;
// Assigning texture to Frame Buffer
unsigned int fbo;
glGenFramebuffers(1, &fbo);
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, image_texture, 0); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, image_texture, 0);
if(glCheckFramebufferStatus(GL_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE){
std::cout<< "Frame buffer is done."<< std::endl;
}
return true;
}
Unfortunately, the above code results in a completely blank screen. I guess, there is something I missed during setting the framebuffer.
Here is the method, where I would like to sample the framebuffer texture by using the mouse coordinates:
void readPixelFromImage(ImVec2 mousePosition) {
unsigned char pixels[4];
glReadBuffer(GL_COLOR_ATTACHMENT0);
glReadPixels(GLint(mousePosition.x), GLint(mousePosition.y), 1, 1, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
std::cout << "r: " << static_cast<int>(pixels[0]) << '\n';
std::cout << "g: " << static_cast<int>(pixels[1]) << '\n';
std::cout << "b: " << static_cast<int>(pixels[2]) << '\n';
std::cout << "a: " << static_cast<int>(pixels[3]) << '\n' << std::endl;
}
Any help is appreciated!
There is indeed something missing in your code:
You set up a new Framebuffer that contains just a single texture buffer. This is okay, so the glCheckFramebufferStatus equals GL_FRAMEBUFFER_COMPLETE. But there is no render buffer attached to your framebuffer. If you want your image rendered on screen, you should use the default framebuffer. This framebuffer is created from your GL context.
However, the documentation says: Default framebuffers cannot change their buffer attachments, [...] https://www.khronos.org/opengl/wiki/Framebuffer. So attaching a texture or renderbuffer to the default FB is certainly not possible. You could, however, generate a new FB as you did, render to it, and finally render the outcome (or blit the buffers) to your default FB. Maybe a good starting point for this technique is https://learnopengl.com/Advanced-Lighting/Deferred-Shading
Moreover, if you intend to just read back rendered values from your GPU, it is more performant to use a renderbuffer instead of a texture. You can even have multiple renderbuffers attached to your framebuffer (as in deferred shading). Example: you could use a second renderbuffer to render an object/instance id (so, the renderbuffer will be single channel integer), and your first renderbuffer will be used for normal drawing. Reading the second renderbuffer with glReadPixels you can directly read which instance was drawn at e.g. the mouse position. This way, you can enable mouse picking very efficiently.
I am attempting to load the following image:
As a texture for the stanford Dragon. The result however is as follows:
I have read that other people have had issues with this due to either not binding the textures correctly or using the wrong number of components when loading a texture. I think that I don't have either of those issues as I am both checking for the format of the image and binding the texture. I have managed to get other images to load correctly, so this seems like there is an issue specific to this image (I am not saying the image is corrupted, rather that something about this image is slightly different to the other images I ahve tried).
The code I am using to initialize the texture is as follows:
//Main constructor
Texture::Texture(string file_path, GLuint t_target)
{
//Change the coordinate system of the image
stbi_set_flip_vertically_on_load(true);
int numComponents;
//Load the pixel data of the image
void *data = stbi_load(file_path.c_str(), &width, &height, &numComponents, 0);
if (data == nullptr)//Error check
{
cerr << "Error when loading texture from file: " + file_path << endl;
Log::record_log(
string(80, '!') +
"\nError when loading texture from file: " + file_path + "\n" +
string(80, '!')
);
exit(EXIT_FAILURE);
}
//Create the texture OpenGL object
target = t_target;
glGenTextures(1, &textureID);
glBindTexture(target, textureID);
//Name the texture
glObjectLabel(GL_TEXTURE, textureID, -1,
("\"" + extract_name(file_path) +"\"").c_str());
//Set the color format
color_format = numComponents == 3 ? GL_RGB : GL_RGBA;
glTexImage2D(target, 0, color_format, width, height, 0,
color_format, GL_UNSIGNED_BYTE, data);
//Set the texture parameters of the image
glTexParameteri(target, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(target, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(target, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(target, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
//free the memory
stbi_image_free(data);
//Create a debug notification event
char name[100];
glGetObjectLabel(GL_TEXTURE, textureID, 100, NULL, name);
string message = "Succesfully created texture: " + string(name) +
". Bound to target: " + textureTargetEnumToString(target);
glDebugMessageInsert(GL_DEBUG_SOURCE_APPLICATION, GL_DEBUG_TYPE_OTHER, 0,
GL_DEBUG_SEVERITY_NOTIFICATION, message.size(), message.c_str());
}
A JPEG eh? Probably no alpha channel then. And 894 pixels wide isn't quite evenly divisible by 4.
Double-check if you're hitting the numComponents == 3 case and if so, make sure GL_UNPACK_ALIGNMENT is set to 1 (default 4) with glPixelStorei() before your glTexImage2D() call.
This question already has answers here:
What are the usual troubleshooting steps for OpenGL textures not showing?
(6 answers)
OpenGL object in C++ RAII class no longer works
(2 answers)
Closed 5 years ago.
I'm trying to create a Texture class for my project which initializes and load a texture from an image. The texture loads well but whenever I want to get the texture ID from outside the class by calling GetTexture() function, glIsTexture() does not consider the return value (the texture ID) as a texture anymore. And the face I want to texture stays blank.
Also, I tried to bind the texture with glBindTexture() directly from the Texture class itself with the function Texture::SetActive() but it still doesn't work.
And finally, when I return the texture ID directly from the function, the texture displays correctly.
Is there something I'm missing here ? I don't really know what to look for at this point.
Thanks in advance for your help !
Here's my Texture class :
// Constructor
Texture::Texture(std::string const& texPath) {
SDL_Surface *texture = nullptr, *newFormatTexture = nullptr, *flippedTexture = nullptr;
SDL_PixelFormat tmpFormat;
Uint32 amask, rmask, gmask, bmask;
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
rmask = 0xFF000000;
gmask = 0x00FF0000;
bmask = 0x0000FF00;
amask = 0x000000FF;
#else
rmask = 0x000000FF;
gmask = 0x0000FF00;
bmask = 0x00FF0000;
amask = 0xFF000000;
#endif
if ((texture = IMG_Load(texPath.c_str())) == nullptr) {
std::cerr << "[ERROR] : Could not load texture " << texPath << ". Skipping..." << std::endl;
}
tmpFormat = *(texture->format);
tmpFormat.BitsPerPixel = 32;
tmpFormat.BytesPerPixel = 4;
tmpFormat.Rmask = rmask;
tmpFormat.Gmask = gmask;
tmpFormat.Bmask = bmask;
tmpFormat.Amask = amask;
if ((newFormatTexture = SDL_ConvertSurface(texture, &tmpFormat, SDL_SWSURFACE)) == nullptr) {
std::cerr << "[ERROR] : Couldn't convert surface to given format." << std::endl;
}
if ((flippedTexture = this->FlipSurface(newFormatTexture)) == nullptr) {
std::cerr << "[ERROR] : Couldn't flip surface." << std::endl;
}
glGenTextures(1, &(this->_textureID));
glBindTexture(GL_TEXTURE_2D, this->_textureID);
glTexImage2D(GL_TEXTURE_2D, 0, 4, flippedTexture->w, flippedTexture->h, 0, GL_RGBA, GL_UNSIGNED_BYTE, flippedTexture->pixels);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glBindTexture(GL_TEXTURE_2D, 0);
SDL_FreeSurface(flippedTexture);
SDL_FreeSurface(newFormatTexture);
SDL_FreeSurface(texture);
}
Texture::Texture(unsigned char *texData, int width, int height) {
glGenTextures(1, &(this->_textureID));
glBindTexture(GL_TEXTURE_2D, this->_textureID);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_LUMINANCE_ALPHA, GL_UNSIGNED_BYTE, texData);
glBindTexture(GL_TEXTURE_2D, 0);
}
Texture::~Texture() {
glDeleteTextures(1, &(this->_textureID));
}
Texture Texture::CreateTexture(std::string const& texPath) {
Texture tex(texPath);
return (tex);
}
Texture Texture::CreateTexture(unsigned char *texData, int width, int height) {
Texture tex(texData, width, height);
return (tex);
}
unsigned int Texture::GetTexture() const {
return (this->_textureID);
}
void Texture::SetActive() {
glBindTexture(GL_TEXTURE_2D, this->_textureID);
}
The main class where I load and use my texture :
int WinMain(void) {
Window window("Hello", 640, 480);
double angleX, angleZ;
Texture tex;
int height;
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(70, (double)640/480, 1, 1000);
glEnable(GL_TEXTURE_2D);
glEnable(GL_DEPTH_TEST);
tex = Texture::CreateTexture("caisse.jpg");
while (!window.Quit()) {
Input::Update();
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(3,4,2,0,0,0,0,0,1);
tex.SetActive();
glBegin(GL_QUADS);
glTexCoord2d(0, 1);
glVertex3d(1, 1, 1);
glTexCoord2d(0, 0);
glVertex3d(1, 1, -1);
glTexCoord2d(1, 0);
glVertex3d(-1, 1, -1);
glTexCoord2d(1, 1);
glVertex3d(-1, 1, 1);
glEnd();
glFlush();
window.RefreshDisplay();
}
return (0);
}
EDIT
I solved my problem.
As described in this topic : What are the usual troubleshooting steps for OpenGL textures not showing? , the initialisation of the texture must not be done in the constructor.
Thanks for the help :)
OK, let's look at this:
Texture Texture::CreateTexture(std::string const& texPath) {
Texture tex(texPath);
return (tex);
}
I'm going to assume that this is a static function. So it creates a Texture object on the stack. And tex contains an OpenGL texture object. The function then returns this object.
By the rules of C++, the lifetime of tex is limited to the scope in which it is created. Namely, Texture::CreateTexture. Which means that, at the end of this function, tex will be destroyed by having its destructor invoked.
But since you returned tex, before that happens, tex will be used to initialize the return value of the function. That return value happens to be an object of type Texture, so the compiler will invoke Texture's copy constructor to initialize the return value.
So, right before tex is destroyed, there are two Texture objects: tex itself and the return value of type Texture that was copied from tex. So far, so good.
Now, tex is destroyed. Texture::~Texture calls glDestroyTexture on the texture object contained within it. That destroys the texture created in the constructor. Fine.
So... what happens now? Well, let's back up to the creation of the return value from CreateTexture. I said that it would invoke the copy constructor of Texture to construct it, passing tex as the object to copy from.
You did not post your complete code, but given the nature of the other code you've written, I'd bet that you didn't write a copy constructor for Texture. That's fine, because the compiler will make one for you.
Only that's not fine. Why? Because right before tex gets destroyed, there are two Texture objects. And both of them store the same OpenGL texture object name. How did that happen?
Because you copied the texture object from tex into the return value. That's what the compiler-generated copy constructor does: it copies everything in the class.
So when tex is destroyed, it is destroying the OpenGL texture it just returned.
Texture should not be a copyable class. It should be move-only, just like many resource-containing classes in C++.
I'm trying to make a very basic example of rendering to the Oculus using their SDK v0.8. All I'm trying to do is render a solid color to both eyes. When I run this, everything appears to initialize correctly. The Oculus shows the health warning message, but all I see is a black screen once the health warning message goes away. What am I doing wrong here?
#define GLEW_STATIC
#include <GL/glew.h>
#define OVR_OS_WIN32
#include <OVR_CAPI_GL.h>
#include <SDL.h>
#include <iostream>
int main(int argc, char *argv[])
{
SDL_Init(SDL_INIT_VIDEO);
SDL_Window* window = SDL_CreateWindow("OpenGL", 100, 100, 800, 600, SDL_WINDOW_OPENGL);
SDL_GLContext context = SDL_GL_CreateContext(window);
//Initialize GLEW
glewExperimental = GL_TRUE;
glewInit();
// Initialize Oculus context
ovrResult result = ovr_Initialize(nullptr);
if (OVR_FAILURE(result))
{
std::cout << "ERROR: Failed to initialize libOVR" << std::endl;
SDL_Quit();
return -1;
}
// Connect to the Oculus headset
ovrSession hmd;
ovrGraphicsLuid luid;
result = ovr_Create(&hmd, &luid);
if (OVR_FAILURE(result))
{
std::cout << "ERROR: Oculus Rift not detected" << std::endl;
SDL_Quit();
return 0;
}
ovrHmdDesc desc = ovr_GetHmdDesc(hmd);
std::cout << "Found " << desc.ProductName << "connected Rift device" << std::endl;
ovrSizei recommenedTex0Size = ovr_GetFovTextureSize(hmd, ovrEyeType(0), desc.DefaultEyeFov[0], 1.0f);
ovrSizei bufferSize;
bufferSize.w = recommenedTex0Size.w;
bufferSize.h = recommenedTex0Size.h;
std::cout << "Buffer Size: " << bufferSize.w << ", " << bufferSize.h << std::endl;
// Generate FBO for oculus
GLuint oculusFbo = 0;
glGenFramebuffers(1, &oculusFbo);
// Create swap texture
ovrSwapTextureSet* pTextureSet = nullptr;
if (ovr_CreateSwapTextureSetGL(hmd, GL_SRGB8_ALPHA8, bufferSize.w, bufferSize.h,&pTextureSet) == ovrSuccess)
{
ovrGLTexture* tex = (ovrGLTexture*)&pTextureSet->Textures[0];
glBindTexture(GL_TEXTURE_2D, tex->OGL.TexId);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
}
// Create ovrLayerHeader
ovrEyeRenderDesc eyeRenderDesc[2];
eyeRenderDesc[0] = ovr_GetRenderDesc(hmd, ovrEye_Left, desc.DefaultEyeFov[0]);
eyeRenderDesc[1] = ovr_GetRenderDesc(hmd, ovrEye_Right, desc.DefaultEyeFov[1]);
ovrLayerEyeFov layer;
layer.Header.Type = ovrLayerType_EyeFov;
layer.Header.Flags = ovrLayerFlag_TextureOriginAtBottomLeft | ovrLayerFlag_HeadLocked;
layer.ColorTexture[0] = pTextureSet;
layer.ColorTexture[1] = pTextureSet;
layer.Fov[0] = eyeRenderDesc[0].Fov;
layer.Fov[1] = eyeRenderDesc[1].Fov;
ovrVector2i posVec;
posVec.x = 0;
posVec.y = 0;
ovrSizei sizeVec;
sizeVec.w = bufferSize.w;
sizeVec.h = bufferSize.h;
ovrRecti rec;
rec.Pos = posVec;
rec.Size = sizeVec;
layer.Viewport[0] = rec;
layer.Viewport[1] = rec;
ovrLayerHeader* layers = &layer.Header;
SDL_Event windowEvent;
while (true)
{
if (SDL_PollEvent(&windowEvent))
{
if (windowEvent.type == SDL_QUIT) break;
}
ovrGLTexture* tex = (ovrGLTexture*)&pTextureSet->Textures[0];
glBindFramebuffer(GL_FRAMEBUFFER, oculusFbo);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, tex->OGL.TexId, 0);
glViewport(0, 0, bufferSize.w, bufferSize.h);
glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
ovr_SubmitFrame(hmd, 0, nullptr, &layers, 1);
SDL_GL_SwapWindow(window);
}
SDL_GL_DeleteContext(context);
SDL_Quit();
return 0;
}
There are a number of problems here
Not initializing ovrLayerEyeFov.RenderPose
Not using ovrSwapTextureSet correctly
Useless calls to SDL_GL_SwapWindow will cause stuttering
Possible undefined behavior when reading the texture while it's still bound for drawing
Not initializing ovrLayerEyeFov.RenderPose
You main problem is that you're not setting the RenderPose member of the ovrLayerEyeFov structure. This member tells the SDK what pose you rendered at and therefore how it should apply timewarp based on the current head pose (which might have changed since you rendered). By not setting this value you're basically giving the SDK a random head pose, which is almost certainly not a valid head pose.
Additionally, ovrLayerFlag_HeadLocked isn't needed for your layer type. It causes the Oculus to display the resulting image in a fixed position relative to your head. It might do what you want, but only if you properly initialize the layer.RenderPose members with the correct values (I'm not sure what those would be in the case of ovrLayerEyeFov, as I've only used the flag in combination with ovrLayerQuad).
What you should do is add the following right after the layer declaration to properly initialize it:
memset(&layer, 0, sizeof(ovrLayerEyeFov));
Then, inside your render loop you should add the following right after the check for a quit event:
ovrTrackingState tracking = ovr_GetTrackingState(hmd, 0, true);
layer.RenderPose[0] = tracking.HeadPose.ThePose;
layer.RenderPose[1] = tracking.HeadPose.ThePose;
This tells the SDK that this image was rendered from the point of view where the head currently is.
Not using ovrSwapTextureSet correctly
Another problem in the code is that you're incorrectly using the texture set. The documentation specifies that when using the texture set, you need to use the texture pointed to by ovrSwapTextureSet.CurrentIndex:
ovrGLTexture* tex = (ovrGLTexture*)(&(pTextureSet->Textures[pTextureSet->CurrentIndex]));
...and then after each call to ovr_SubmitFrame you need to increment ovrSwapTextureSet.CurrentIndex then mod the value by ovrSwapTextureSet.TextureCount like so
pTextureSet->CurrentIndex = (pTextureSet->CurrentIndex + 1) % pTextureSet->TextureCount;
Useless calls to SDL_GL_SwapWindow will cause stuttering
The SDL_GL_SwapWindow(window); call is unnecessary and pointless since you haven't drawn anything to the default framebuffer. Once you move away from drawing a solid color, this call will end up causing judder, since it will block until v-sync (typically at 60hz) causing you to sometimes miss the refersh of the Oculus display. Right now this will be invisible because your scene is just a solid color, but later on when you're rendering objects in 3D, it will cause intolerable judder.
You can use SDL_GL_SwapWindow if you
Ensure v-sync is disabled
Have a mirror texture available to draw to the window. (See the documentation for ovr_CreateMirrorTextureGL)
Possible framebuffer issues
I'm less certain about this one being a serious problem, but I would also suggest unbinding the framebuffer and detaching the Oculus provided texture before sending it to ovr_SubmitFrame(), as I'm not certain that the behavior is well defined when reading from a texture attached to a framebuffer that is currently bound for drawing. It seems to have no impact on my local system, but undefined doesn't mean doesn't work, it just means you can't rely on it to work.
I've updated the sample code and put it here. As a bonus I've modified it so it draws one color on the left eye and a different color on the right eye, as well as setting up the buffer to provide for rendering one half of the buffer for each eye.
I'm attempting to render a .png image as a texture. However, all that is being rendered is a white square.
I give my texture a unique int ID called texID, read the pixeldata into a buffer 'image' (declared in the .h file). I load my pixelbuffer, do all of my OpenGL stuff and bind that pixelbuffer to a texture for OpenGL. I then draw it all using glDrawElements.
Also I initialize the texture with a size of 32x32 when its contructor is called, therefore i doubt it is related to a power of two size issue.
Can anybody see any mistakes in my OpenGL GL_TEXTURE_2D setup that might give me a block white square.
#include "Texture.h"
Texture::Texture(int width, int height, string filename)
{
const char* fnPtr = filename.c_str(); //our image loader accepts a ptr to a char, not a string
printf(fnPtr);
w = width; //give our texture a width and height, the reason that we need to pass in the width and height values manually
h = height;//UPDATE, these MUST be P.O.T.
unsigned error = lodepng::decode(image,w,h,fnPtr);//lodepng's decode function will load the pixel data into image vector
//display any errors with the texture
if(error)
{
cout << "\ndecoder error " << error << ": " << lodepng_error_text(error) <<endl;
}
for(int i = 0; i<image.size(); i++)
{
printf("%i,", image.at(i));
}
printf("\nImage size is %i", image.size());
//image now contains our pixeldata. All ready for OpenGL to do its thing
//let's get this texture up in the video memory
texGLInit();
}
void Texture::texGLInit()
{
//WHERE YOU LEFT OFF: glGenTextures isn't assigning an ID to textures. it stays at zero the whole time
//i believe this is why it's been rendering white
glGenTextures(1, &textures);
printf("\ntexture = %u", textures);
glBindTexture(GL_TEXTURE_2D, textures);//evrything we're about to do is about this texture
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
//glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
//glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
//glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
//glDisable(GL_COLOR_MATERIAL);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8,w,h,0, GL_RGBA, GL_UNSIGNED_BYTE, &image);
//we COULD free the image vectors memory right about now.
}
void Texture::draw(point centerPoint, point dimensions)
{
glEnable(GL_TEXTURE_2D);
printf("\nDrawing block at (%f, %f)",centerPoint.x, centerPoint.y);
glBindTexture(GL_TEXTURE_2D, textures);//bind the texture
//create a quick vertex array for the primitive we're going to bind the texture to
printf("TexID = %u",textures);
GLfloat vArray[8] =
{
centerPoint.x-(dimensions.x/2), centerPoint.y-(dimensions.y/2),//bottom left i0
centerPoint.x-(dimensions.x/2), centerPoint.y+(dimensions.y/2),//top left i1
centerPoint.x+(dimensions.x/2), centerPoint.y+(dimensions.y/2),//top right i2
centerPoint.x+(dimensions.x/2), centerPoint.y-(dimensions.y/2)//bottom right i3
};
//create a quick texture array (we COULD create this on the heap rather than creating/destoying every cycle)
GLfloat tArray[8] =
{
0.0f,0.0f, //0
0.0f,1.0f, //1
1.0f,1.0f, //2
1.0f,0.0f //3
};
//and finally.. the index array...remember, we draw in triangles....(and we'll go CW)
GLubyte iArray[6] =
{
0,1,2,
0,2,3
};
//Activate arrays
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
//Give openGL a pointer to our vArray and tArray
glVertexPointer(2, GL_FLOAT, 0, &vArray[0]);
glTexCoordPointer(2, GL_FLOAT, 0, &tArray[0]);
//Draw it all
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_BYTE, &iArray[0]);
//glDrawArrays(GL_TRIANGLES,0,6);
//Disable the vertex arrays
glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
glDisable(GL_TEXTURE_2D);
//done!
/*glBegin(GL_QUADS);
glTexCoord2f(0.0f,0.0f);
glVertex2f(centerPoint.x-(dimensions.x/2), centerPoint.y-(dimensions.y/2));
glTexCoord2f(0.0f,1.0f);
glVertex2f(centerPoint.x-(dimensions.x/2), centerPoint.y+(dimensions.y/2));
glTexCoord2f(1.0f,1.0f);
glVertex2f(centerPoint.x+(dimensions.x/2), centerPoint.y+(dimensions.y/2));
glTexCoord2f(1.0f,0.0f);
glVertex2f(centerPoint.x+(dimensions.x/2), centerPoint.y-(dimensions.y/2));
glEnd();*/
}
Texture::Texture(void)
{
}
Texture::~Texture(void)
{
}
I'll also include the main class' init, where I do a bit more OGL setup before this.
void init(void)
{
printf("\n......Hello Guy. \n....\nInitilising");
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0,XSize,0,YSize);
glEnable(GL_TEXTURE_2D);
myBlock = new Block(0,0,offset);
glClearColor(0,0.4,0.7,1);
glLineWidth(2); // Width of the drawing line
glMatrixMode(GL_MODELVIEW);
glDisable(GL_DEPTH_TEST);
printf("\nInitialisation Complete");
}
Update: adding in the main function where I first setup my OpenGL window.
int main(int argc, char** argv)
{
glutInit(&argc, argv); // GLUT Initialization
glutInitDisplayMode(GLUT_RGBA|GLUT_DOUBLE); // Initializing the Display mode
glutInitWindowSize(800,600); // Define the window size
glutCreateWindow("Gem Miners"); // Create the window, with caption.
printf("\n========== McLeanTech Systems =========\nBecoming Sentient\n...\n...\n....\nKILL\nHUMAN\nRACE \n");
init(); // All OpenGL initialization
//-- Callback functions ---------------------
glutDisplayFunc(display);
glutKeyboardFunc(mykey);
glutSpecialFunc(processSpecialKeys);
glutSpecialUpFunc(processSpecialUpKeys);
//glutMouseFunc(mymouse);
glutMainLoop(); // Loop waiting for event
}
Here's the usual checklist for whenever textures come out white:
OpenGL context created and being bound to current thread when attemting to load texture?
Allocated texture ID using glGenTextures?
Are the parameters format and internal format to glTex[Sub]Image… valid OpenGL tokens allowed as input for this function?
Is mipmapping being used?
YES: Supply all mipmap layers – optimally set glTexParameteri GL_TEXTURE_BASE_LEVEL and GL_TEXTURE_MAX_LEVEL, as well as GL_TEXTURE_MIN_LOD and GL_TEXTURE_MAX_LOG.
NO: Turn off mipmap filtering by setting glTexParameteri GL_TEXTURE_MIN_FILTER to GL_NEAREST or GL_LINEAR.