Sign in to follow this  
redneon

OpenGL OpenGL ES 2 Texture Not Rendering

Recommended Posts

I'm porting my game framework from OpenGL 3/4 to OpenGL ES 2 but I'm having an issue where textures aren't being rendered.

In once instance I'm using simple vertex buffer objects to store the vertices and texcoords. In my OpenGL code these are bound in vertex arrays but I understand they aren't used in ES. Basically, I have some initialisation code where I do this:

[source lang="cpp"]
//glGenVertexArrays(1, &m_vao); //Not used in GLES.
glGenBuffers(2, m_vbo);

//glBindVertexArray(m_vao); //Not used in GLES.

glBindBuffer(GL_ARRAY_BUFFER, m_vbo[0]);
glBufferData(GL_ARRAY_BUFFER, 4 * sizeof(Vector2), ms_verts, GL_STATIC_DRAW);

glBindBuffer(GL_ARRAY_BUFFER, m_vbo[1]);
glBufferData(GL_ARRAY_BUFFER, 4 * sizeof(Vector2), ms_texCoords, GL_STATIC_DRAW);
[/source]

And then when it comes time to render I do this:

[source lang="cpp"]

int32_t* pUniformHandle = m_uniforms.Find(textureParamName);

if (pUniformHandle)
{
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, m_textureHandle);
glUniform1i(*pUniformHandle, 0);
}

//glBindVertexArray(m_vao); //Not used in GLES.

glBindBuffer(GL_ARRAY_BUFFER, m_vbo[0]);
glVertexAttribPointer(Effect::POSITION_ATTR, 2, GL_FLOAT, GL_FALSE, 0, 0);
glEnableVertexAttribArray(Effect::POSITION_ATTR);

glBindBuffer(GL_ARRAY_BUFFER, m_vbo[1]);
glVertexAttribPointer(Effect::TEXCOORD0_ATTR, 2, GL_FLOAT, GL_FALSE, 0, 0);
glEnableVertexAttribArray(Effect::TEXCOORD0_ATTR);

glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

glDisableVertexAttribArray(Effect::TEXCOORD0_ATTR);
glDisableVertexAttribArray(Effect::POSITION_ATTR);
[/source]

In OpenGL (with those "Not used in GLES" bits uncommented) this works fine but in GLES the prims are being rendered but the texture isn't being applied. For reference, my shader looks like this:

Vertex shader:

[source lang="plain"]
uniform mat4 worldMatrix;
uniform mat4 projectionMatrix;

attribute vec2 aPosition;
attribute vec2 aTexCoord;

varying vec2 vTexCoord;

void main()
{
vTexCoord = aTexCoord;
mat4 worldProjMatrix = projectionMatrix * worldMatrix;
gl_Position = worldProjMatrix * vec4(aPosition, 0.0, 1.0);
}
[/source]

Fragment shader:

[source lang="plain"]
uniform sampler2D texture;
uniform vec4 colour;

varying vec2 vTexCoord;

void main()
{
gl_FragColor = texture2D(texture, vTexCoord) * colour;
}
[/source]

Can anyone see what I'm doing wrong? I've been scanning through the GLES book but I can't see anything obvious.

Share this post


Link to post
Share on other sites
[quote name='redneon' timestamp='1341001825' post='4954077']
In OpenGL (with those "Not used in GLES" bits uncommented) this works fine but in GLES the prims are being rendered but the texture isn't being applied
[/quote]

To be precise, there is no such thing 'the texture isn't being applied'. What do you mean exactly? The geometry renders properly, but all rasterized fragments come out black (i.e. the texture2D call in the shader comes out black) ?

I have run into such cases several times with GLES2, and searching the codebase, I find I have added these checks:

[code]


/* GLES2 Tegra2(?) bug:
If you specify wrap for texture S coordinate and clamp for texture T coordinate, and the texture width is pow2,
but height is not, the wrap operation will silently fail and be treated as a clamp operation.
*/

/* Sanity check to avoid GLES2 SILENT FAILURES: http://www.khronos.org/opengles/sdk/docs/man/xhtml/glTexParameter.xml
If the texture does not have mipmaps, specifying MIN filter of GL_xxx_MIPMAP_xxx will succeed, but silently
render black. */
const bool hasMipmaps = targetTexture->NumMipmaps() > 1;

if (hasMipmaps)
{
if (!IsPow2(targetTexture->Width()) || !IsPow2(targetTexture->Height()))
{
LOGE("ApplyTextureSampler Error: GLES2 will now silently render black since mipmapping was specified for a non-pow2 texture! Killing mipmaps from texture '%s' as a workaround.",
targetTexture->Name().c_str());
targetTexture->DisableMipmaps();
}
}
[/code]

[code]

/* Sanity check to detect GLES2 SILENT FAILURES: http://www.khronos.org/opengles/sdk/docs/man/xhtml/glTexParameter.xml
" if the width or height of a texture image are not powers of two and either the
GL_TEXTURE_MIN_FILTER is set to one of the functions that requires mipmaps or the GL_TEXTURE_WRAP_S or
GL_TEXTURE_WRAP_T is not set to GL_CLAMP_TO_EDGE, then the texture image unit will return
(R, G, B, A) = (0, 0, 0, 1). " */
if ((textureSampler->addressU != TextureAddressClamp || textureSampler->addressV != TextureAddressClamp) && (!IsPow2(targetTexture->Width()) || !IsPow2(targetTexture->Height())))
LOGE("ApplyTextureSampler Error: GLES2 doesn't support other addressing modes than GL_CLAMP_TO_EDGE when size is not pow2! Size was %dx%d in texture '%s'. (GLES2 will now silently render black)",
targetTexture->Width(), targetTexture->Height(), targetTexture->Name().c_str());
[/code]

The page http://www.khronos.org/opengles/sdk/docs/man/xhtml/glTexParameter.xml documents
[quote]

Suppose that a texture is accessed from a fragment shader or vertex shader and has set GL_TEXTURE_MIN_FILTER to one of the functions that requires mipmaps. If either the dimensions of the texture images currently defined (with previous calls to glTexImage2D, glCompressedTexImage2D, or glCopyTexImage2D) do not follow the proper sequence for mipmaps (described above), or there are fewer texture images defined than are needed, or the set of texture images were defined with different formats or types, then the texture image unit will return (R, G, B, A) = (0, 0, 0, 1).

Similarly, if the width or height of a texture image are not powers of two and either the GL_TEXTURE_MIN_FILTER is set to one of the functions that requires mipmaps or the GL_TEXTURE_WRAP_S or GL_TEXTURE_WRAP_T is not set to GL_CLAMP_TO_EDGE, then the texture image unit will return (R, G, B, A) = (0, 0, 0, 1).
[/quote]

Needless to say, the very existence of documented silent failure cases for an API (combined with the lack of a documented way to set up a debug mode that would properly detect these) is a major picard facepalm.jpg situation.

Share this post


Link to post
Share on other sites
[quote name='clb' timestamp='1341007126' post='4954112']
[color=#282828][font=helvetica, arial, verdana, tahoma, sans-serif][size=3][left][background=rgb(250, 251, 252)]To be precise, there is no such thing 'the texture isn't being applied'. What do you mean exactly? The geometry renders properly, but all rasterized fragments come out black (i.e. the texture2D call in the shader comes out black) ?[/background][/left][/size][/font][/color]
[/quote]

Sorry, yes, I was generalising as I wrote the post quickly but yeah the geometry renders correctly but black. If I change the fragment shader to output a defined colour like, say gl_FragColour = vec4(1.0, 0.0, 0.0, 1.0); then it renders with the colour I supplied instead of black. But when I use the texture2D function I just get black prims.

The particular texture I'm trying to display is 512x512 so that rules out the power of two thing. I've also just tried setting GL_TEXTURE_WRAP_S and GL_TEXTURE_WRAP_T to GL_CLAMP_TO_EDGE and GL_TEXTURE_MIN_FILTER and FL_TEXTURE_MAG_FILTER to GL_LINEAR but it hasn't made a difference.

Also, not sure if it makes a difference but I am using ATI's GLES SDK in Windows. My plan was to get it working in Windows, so I know it's working, before I move it across to my Raspberry Pi, which is my ultimate goal.

I'll have more of a look tomorrow as I'm done for tonight.

Share this post


Link to post
Share on other sites
The OpenGL ES 2 Windows® SDK’s do not work exactly the same as on real devices, but you should at least be able to display textures.

There can be many reasons for getting black textures.[list=1]
[*][s]If mipmaps are enabled but the image does not have a full mipmap chain supplied (full meaning down to 1×1).[/s]
[*][s]If the texture is not a power of 2 and the wrap modes are not set to GL_CLAMP_TO_EDGE.[/s]
[*][s]If the texture is not being activated in the appropriate slot.[/s]
[*][s]If the sampler has not been assigned to that slot.[/s]
[*]If the texture coordinates are absent or incorrect.
[*]If “colour” has not been assigned.
[/list]

I give you the benefit of a doubt on #4, since I see code that is attempting to set the sampler to 0, but I have no way of knowing if the handle is actually valid or not. But samplers default to 0 anyway so that won’t be your problem.

Which means you have 2 more things to test.
Test #5 by printing the texture coordinates.

[CODE]gl_FragColor = vec4( vTexCoord.x, vTexCoord.y, 0.0, 1.0 );[/CODE]

Test #6 by removing “colour” from the equation. I don’t see anywhere where you are setting that value.


L. Spiro

Share this post


Link to post
Share on other sites
I like #5, it's a clever way of seeing the texture coordinates are valid. Alas, mine were, black top-left, red top-right, green bottom-left, yellow bottom-right.

I am setting the colour value (though I know in my code I only showed me setting the texture uniform) but just to double check I removed colour from the gl_FragColor calculation and I'm still getting a black square.

I did think perhaps something isn't working in the GLES Windows SDK and that I should just port my code to Pi and fix the issue on there, if it's still an issue. That being said, if I run the Simple_Texture2D sample from the GLES book then the texture displays correctly. The only difference I can see between my code and theirs, however, is that they use glVertexAttribPointer to send the data to the GPU each render instead of storing the data off in a VBO. Should this make a difference? Edited by redneon

Share this post


Link to post
Share on other sites
I just quickly tried sacking off the VBOs and using glVertexAttribPointer to send the data to the GPU each render, as in the Simple_Texture2D sample like this:

[source lang="cpp"]
glVertexAttribPointer(Effect::POSITION_ATTR, 2, GL_FLOAT, GL_FALSE, 0, ms_verts);
glVertexAttribPointer(Effect::TEXCOORD0_ATTR, 2, GL_FLOAT, GL_FALSE, 0, ms_texCoords);

glEnableVertexAttribArray(Effect::POSITION_ATTR);
glEnableVertexAttribArray(Effect::TEXCOORD0_ATTR);

glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

glDisableVertexAttribArray(Effect::TEXCOORD0_ATTR);
glDisableVertexAttribArray(Effect::POSITION_ATTR);
[/source]

But now even the geometry isn't being rendered. I've probably done something stupid but I only had a quick five minutes before I go to work so I thought I'd give it a try. I'll have more of a look when I get back from work.

Share this post


Link to post
Share on other sites
I've fixed why the geometry wasn't being rendered when I don't use VBOs (I was being an idiot and hadn't unbound a buffer I was using elsewhere). So, I've got the geometry rending both with and without VBOs but in both instances I'm just getting black prims without the texture.

I'm now trying to match my code as closely as possible to the Simple_Texture2D sample. The first step was removing the VBOs, I've also tried using their texture code too but it hasn't made a difference. There must be something obviously different between my code and theirs though, for theirs to be working and mine not. I'm sure I'll get to the bottom of it if I keep chugging away :)

Share this post


Link to post
Share on other sites
Just thinking, is there any chance that I could have set my window up incorrectly? Maybe something wrong in the EGL stuff? I don't think that this could cause this issue but I'm just clutching at straws really, as I can't see any difference between my code and the Simple_Texture2D code.

Share this post


Link to post
Share on other sites
Try assuming that it is an asset difference rather than a code difference. Try with a known working texture asset. Or try starting from the working sample and try to evolve it towards your breaking testcase one by one to see where it breaks.

I don't think there's anything in the EGL spec that would affect how texture2D sampling is done in the shader code.

Share this post


Link to post
Share on other sites
Bloody hell. I've fixed it and, as per usual with these things, it was user error. I was passing an incorrect value into glTexImage2D for the internal format. If you look at my texture load code below you can see I'm incorrectly passing bitDepth into glTexImage2D instead of textureFormat. Doh! I've no idea how this works correctly in normal OpenGL, though. I would expect it to fail like it does in GLES. Ah well, nevermind.
[source lang="cpp"]int32_t width, height, bitDepth = 0;
//Load the image.
uint8_t* pData = ::stbi_load_from_memory(rTextureFile.GetData(), rTextureFile.GetSize(), &width, &height, &bitDepth, 0);

if (pData)
{
m_width = width;
m_height = height;
m_bitDepth = bitDepth;

uint32_t textureFormat = bitDepth == 4 ? GL_RGBA : GL_RGB;
glGenTextures(1, &m_handle);
glBindTexture(GL_TEXTURE_2D, m_handle);
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,
bitDepth,
width,
height,
0,
textureFormat,
GL_UNSIGNED_BYTE,
pData);

//No longer need the image.
stbi_image_free(pData);

return true;
}

return false;
[/source]
Thanks for your help, everyone.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Announcements

  • Forum Statistics

    • Total Topics
      628303
    • Total Posts
      2981923
  • Similar Content

    • By mellinoe
      Hi all,
      First time poster here, although I've been reading posts here for quite a while. This place has been invaluable for learning graphics programming -- thanks for a great resource!
      Right now, I'm working on a graphics abstraction layer for .NET which supports D3D11, Vulkan, and OpenGL at the moment. I have implemented most of my planned features already, and things are working well. Some remaining features that I am planning are Compute Shaders, and some flavor of read-write shader resources. At the moment, my shaders can just get simple read-only access to a uniform (or constant) buffer, a texture, or a sampler. Unfortunately, I'm having a tough time grasping the distinctions between all of the different kinds of read-write resources that are available. In D3D alone, there seem to be 5 or 6 different kinds of resources with similar but different characteristics. On top of that, I get the impression that some of them are more or less "obsoleted" by the newer kinds, and don't have much of a place in modern code. There seem to be a few pivots:
      The data source/destination (buffer or texture) Read-write or read-only Structured or unstructured (?) Ordered vs unordered (?) These are just my observations based on a lot of MSDN and OpenGL doc reading. For my library, I'm not interested in exposing every possibility to the user -- just trying to find a good "middle-ground" that can be represented cleanly across API's which is good enough for common scenarios.
      Can anyone give a sort of "overview" of the different options, and perhaps compare/contrast the concepts between Direct3D, OpenGL, and Vulkan? I'd also be very interested in hearing how other folks have abstracted these concepts in their libraries.
    • By aejt
      I recently started getting into graphics programming (2nd try, first try was many years ago) and I'm working on a 3d rendering engine which I hope to be able to make a 3D game with sooner or later. I have plenty of C++ experience, but not a lot when it comes to graphics, and while it's definitely going much better this time, I'm having trouble figuring out how assets are usually handled by engines.
      I'm not having trouble with handling the GPU resources, but more so with how the resources should be defined and used in the system (materials, models, etc).
      This is my plan now, I've implemented most of it except for the XML parts and factories and those are the ones I'm not sure of at all:
      I have these classes:
      For GPU resources:
      Geometry: holds and manages everything needed to render a geometry: VAO, VBO, EBO. Texture: holds and manages a texture which is loaded into the GPU. Shader: holds and manages a shader which is loaded into the GPU. For assets relying on GPU resources:
      Material: holds a shader resource, multiple texture resources, as well as uniform settings. Mesh: holds a geometry and a material. Model: holds multiple meshes, possibly in a tree structure to more easily support skinning later on? For handling GPU resources:
      ResourceCache<T>: T can be any resource loaded into the GPU. It owns these resources and only hands out handles to them on request (currently string identifiers are used when requesting handles, but all resources are stored in a vector and each handle only contains resource's index in that vector) Resource<T>: The handles given out from ResourceCache. The handles are reference counted and to get the underlying resource you simply deference like with pointers (*handle).  
      And my plan is to define everything into these XML documents to abstract away files:
      Resources.xml for ref-counted GPU resources (geometry, shaders, textures) Resources are assigned names/ids and resource files, and possibly some attributes (what vertex attributes does this geometry have? what vertex attributes does this shader expect? what uniforms does this shader use? and so on) Are reference counted using ResourceCache<T> Assets.xml for assets using the GPU resources (materials, meshes, models) Assets are not reference counted, but they hold handles to ref-counted resources. References the resources defined in Resources.xml by names/ids. The XMLs are loaded into some structure in memory which is then used for loading the resources/assets using factory classes:
      Factory classes for resources:
      For example, a texture factory could contain the texture definitions from the XML containing data about textures in the game, as well as a cache containing all loaded textures. This means it has mappings from each name/id to a file and when asked to load a texture with a name/id, it can look up its path and use a "BinaryLoader" to either load the file and create the resource directly, or asynchronously load the file's data into a queue which then can be read from later to create the resources synchronously in the GL context. These factories only return handles.
      Factory classes for assets:
      Much like for resources, these classes contain the definitions for the assets they can load. For example, with the definition the MaterialFactory will know which shader, textures and possibly uniform a certain material has, and with the help of TextureFactory and ShaderFactory, it can retrieve handles to the resources it needs (Shader + Textures), setup itself from XML data (uniform values), and return a created instance of requested material. These factories return actual instances, not handles (but the instances contain handles).
       
       
      Is this a good or commonly used approach? Is this going to bite me in the ass later on? Are there other more preferable approaches? Is this outside of the scope of a 3d renderer and should be on the engine side? I'd love to receive and kind of advice or suggestions!
      Thanks!
    • By nedondev
      I 'm learning how to create game by using opengl with c/c++ coding, so here is my fist game. In video description also have game contain in Dropbox. May be I will make it better in future.
      Thanks.
    • By Abecederia
      So I've recently started learning some GLSL and now I'm toying with a POM shader. I'm trying to optimize it and notice that it starts having issues at high texture sizes, especially with self-shadowing.
      Now I know POM is expensive either way, but would pulling the heightmap out of the normalmap alpha channel and in it's own 8bit texture make doing all those dozens of texture fetches more cheap? Or is everything in the cache aligned to 32bit anyway? I haven't implemented texture compression yet, I think that would help? But regardless, should there be a performance boost from decoupling the heightmap? I could also keep it in a lower resolution than the normalmap if that would improve performance.
      Any help is much appreciated, please keep in mind I'm somewhat of a newbie. Thanks!
    • By test opty
      Hi,
      I'm trying to learn OpenGL through a website and have proceeded until this page of it. The output is a simple triangle. The problem is the complexity.
      I have read that page several times and tried to analyse the code but I haven't understood the code properly and completely yet. This is the code:
       
      #include <glad/glad.h> #include <GLFW/glfw3.h> #include <C:\Users\Abbasi\Desktop\std_lib_facilities_4.h> using namespace std; //****************************************************************************** void framebuffer_size_callback(GLFWwindow* window, int width, int height); void processInput(GLFWwindow *window); // settings const unsigned int SCR_WIDTH = 800; const unsigned int SCR_HEIGHT = 600; const char *vertexShaderSource = "#version 330 core\n" "layout (location = 0) in vec3 aPos;\n" "void main()\n" "{\n" " gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n" "}\0"; const char *fragmentShaderSource = "#version 330 core\n" "out vec4 FragColor;\n" "void main()\n" "{\n" " FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n" "}\n\0"; //******************************* int main() { // glfw: initialize and configure // ------------------------------ glfwInit(); glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3); glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3); glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); // glfw window creation GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "My First Triangle", nullptr, nullptr); if (window == nullptr) { cout << "Failed to create GLFW window" << endl; glfwTerminate(); return -1; } glfwMakeContextCurrent(window); glfwSetFramebufferSizeCallback(window, framebuffer_size_callback); // glad: load all OpenGL function pointers if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) { cout << "Failed to initialize GLAD" << endl; return -1; } // build and compile our shader program // vertex shader int vertexShader = glCreateShader(GL_VERTEX_SHADER); glShaderSource(vertexShader, 1, &vertexShaderSource, nullptr); glCompileShader(vertexShader); // check for shader compile errors int success; char infoLog[512]; glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success); if (!success) { glGetShaderInfoLog(vertexShader, 512, nullptr, infoLog); cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << endl; } // fragment shader int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER); glShaderSource(fragmentShader, 1, &fragmentShaderSource, nullptr); glCompileShader(fragmentShader); // check for shader compile errors glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success); if (!success) { glGetShaderInfoLog(fragmentShader, 512, nullptr, infoLog); cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << endl; } // link shaders int shaderProgram = glCreateProgram(); glAttachShader(shaderProgram, vertexShader); glAttachShader(shaderProgram, fragmentShader); glLinkProgram(shaderProgram); // check for linking errors glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success); if (!success) { glGetProgramInfoLog(shaderProgram, 512, nullptr, infoLog); cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << endl; } glDeleteShader(vertexShader); glDeleteShader(fragmentShader); // set up vertex data (and buffer(s)) and configure vertex attributes float vertices[] = { -0.5f, -0.5f, 0.0f, // left 0.5f, -0.5f, 0.0f, // right 0.0f, 0.5f, 0.0f // top }; unsigned int VBO, VAO; glGenVertexArrays(1, &VAO); glGenBuffers(1, &VBO); // bind the Vertex Array Object first, then bind and set vertex buffer(s), //and then configure vertex attributes(s). glBindVertexArray(VAO); glBindBuffer(GL_ARRAY_BUFFER, VBO); glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0); glEnableVertexAttribArray(0); // note that this is allowed, the call to glVertexAttribPointer registered VBO // as the vertex attribute's bound vertex buffer object so afterwards we can safely unbind glBindBuffer(GL_ARRAY_BUFFER, 0); // You can unbind the VAO afterwards so other VAO calls won't accidentally // modify this VAO, but this rarely happens. Modifying other // VAOs requires a call to glBindVertexArray anyways so we generally don't unbind // VAOs (nor VBOs) when it's not directly necessary. glBindVertexArray(0); // uncomment this call to draw in wireframe polygons. //glPolygonMode(GL_FRONT_AND_BACK, GL_LINE); // render loop while (!glfwWindowShouldClose(window)) { // input // ----- processInput(window); // render // ------ glClearColor(0.2f, 0.3f, 0.3f, 1.0f); glClear(GL_COLOR_BUFFER_BIT); // draw our first triangle glUseProgram(shaderProgram); glBindVertexArray(VAO); // seeing as we only have a single VAO there's no need to // bind it every time, but we'll do so to keep things a bit more organized glDrawArrays(GL_TRIANGLES, 0, 3); // glBindVertexArray(0); // no need to unbind it every time // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.) glfwSwapBuffers(window); glfwPollEvents(); } // optional: de-allocate all resources once they've outlived their purpose: glDeleteVertexArrays(1, &VAO); glDeleteBuffers(1, &VBO); // glfw: terminate, clearing all previously allocated GLFW resources. glfwTerminate(); return 0; } //************************************************** // process all input: query GLFW whether relevant keys are pressed/released // this frame and react accordingly void processInput(GLFWwindow *window) { if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS) glfwSetWindowShouldClose(window, true); } //******************************************************************** // glfw: whenever the window size changed (by OS or user resize) this callback function executes void framebuffer_size_callback(GLFWwindow* window, int width, int height) { // make sure the viewport matches the new window dimensions; note that width and // height will be significantly larger than specified on retina displays. glViewport(0, 0, width, height); } As you see, about 200 lines of complicated code only for a simple triangle. 
      I don't know what parts are necessary for that output. And also, what the correct order of instructions for such an output or programs is, generally. That start point is too complex for a beginner of OpenGL like me and I don't know how to make the issue solved. What are your ideas please? What is the way to figure both the code and the whole program out correctly please?
      I wish I'd read a reference that would teach me OpenGL through a step-by-step method. 
  • Popular Now