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mynameisnafe

OpenGL
I feel like a Noob C++ GL 4.1 and GLSL 3.3 help please!

13 posts in this topic

Please help! I am trying to render a textured quad.
For the life of me, it retains black with a textured phong shader. In fact, when I use a phong shader, it stays black, even though its the same phong shader that renders all the models around said dastardly quad.

I'm hoping the code is quite explanatory so I'm just gonna walk through it and someone with a sharper eye than I can hunt for glory. Beware, there is a LOT of code - just looked and I feel bad.. however I do have to explain a couple of classes, FreeImage, and how it all works. I have quite a big project now.. it just doesn't yet do a lot because I don't have any textures. Just some 30-second -to-load .objs that are blue, and almost shiny.

 

I digress, the 'textured' quad gets made with the line below, which calls CreateQuad inline. It's gonna have some picture of some wood or something on it. It sits at 5,5,0 world space, and is 5x5 units in area.

m_HUD->Create( *ShapeFactory::CreateQuad( 5, 5, 5, 5, true),
	         "../Shaders/basic_phong.vs", "../Shaders/basic_phong.fs" );

Heres CreateQuad. (I post this so you can spot an error in it, but it ~should~ be pretty standard. It creates a quad. I hope.)

GeometryData* // Draw with GL_QUADS, centred on x, y
	ShapeFactory::CreateQuad(int x, int y, int width, int height, bool textured)
{
	GeometryData* shape = new GeometryData();
	shape->SetTopology(7); // ..->SetTopology(GL_QUADS);
	
	float x0, x1, y0, y1;
	
	x0 = x + (width/2);	x1 = x - (width/2);
	y0 = y + (height/2);	y1 = y - (height/2);

	shape->numVertices = 4;
	shape->m_Vertices = (Cream::Vertex3D*) calloc (4, sizeof(Cream::Vertex3D) );
	shape->m_Vertices[0] = Vertex3D( x0, y1 , 0.0f );
	shape->m_Vertices[1] = Vertex3D( x1, y1 , 0.0f );
	shape->m_Vertices[2] = Vertex3D( x1, y0 , 0.0f );
	shape->m_Vertices[3] = Vertex3D( x0, y0 , 0.0f );

	shape->numNormals = 4;	
	shape->m_Normals = (Cream::Vertex3D*) calloc (4, sizeof(Cream::Vertex3D) );
	shape->m_Normals[0] = Vertex3D( 0.0f, 0.0f , 1.0f );
	shape->m_Normals[1] = Vertex3D( 0.0f, 0.0f , 1.0f );
	shape->m_Normals[2] = Vertex3D( 0.0f, 0.0f , 1.0f );
	shape->m_Normals[3] = Vertex3D( 0.0f, 0.0f , 1.0f );

	if( textured )
	{
		shape->numUVs = 4;
		shape->m_TexCoords = (Cream::Vertex2D*) calloc (4, sizeof(Cream::Vertex2D) );
		shape->m_TexCoords[0] = Vertex2D(0.0f, 1.0f);
		shape->m_TexCoords[1] = Vertex2D(1.0f, 1.0f);
		shape->m_TexCoords[2] = Vertex2D(1.0f, 0.0f);
		shape->m_TexCoords[3] = Vertex2D(0.0f, 0.0f);
	}

	shape->numIndices = 0;

	return shape;	
}

m_HUD is of type GLMesh. GLMesh::Create in short creates a VAO from that GeometryData, a Shader from those filenames, and holds a material - which contains uniforms I may want to set for the model; colour, gl texture id, texture name, etc. It has the Render method.

So, GLMesh::PreRender sets uniforms by talking to its GLShader, and it works like this: If the material says I'm textured, if it contains a texture ID for a diffuse map -- then I have a KdID, I set it. It also sets camera matrices. bOk is bOk, whether I use a texture or no, so the "1" is getting sent to map_kd in the shader.

if(material->isTextured)
{
	if( material->KdID != 0 )
	{	// both barrels and still nothing!
		glActiveTexture(GL_TEXTURE1);
		glBindTexture(GL_TEXTURE_2D, material->KdID );

		bOk = bOk && m_Shader->SetUniformInt( 1, "map_kd" );
	}
	if( material->KaID != 0 )
	{
		//glActiveTexture(GL_TEXTURE2);
		glBindTexture(GL_TEXTURE_2D, material->KaID );
	
        	bOk = bOk && m_Shader->SetUniformInt( 2, "map_ka" );		
	}
        ......
        else
        {       // always fires for non-textured shader, always works*
                bOk = bOk && m_Shader->SetUniformVec4(glm::vec4(material->Kd.GLM(), 1.0), "m_Kd");
        }

So that explains how the quad gets made and how it gets rendered, using texture unit or colour, the other data that it requires etc to exist in GL land. I'm pretty sure everything's good except setting the texture / sampler (I've said little of textures, I know).

 

I got FreeImage. It gives me bits, and I copy them, and keep them locally, then I let GL copy them and GL gives me a texture unit.

 

It gets convoluted though - as I said, I keep the texture locally and don't free them bits after I give them to OpenGL, because I want to play later - so I have a class for a texture, that lets me access those bits from FreeImage with GetPixel, SetPixel, Fill, etc, as if it were a 2D array. This I feel would be a handy thing to make heightmaps with, among other things.

So FreeImage gives me bits, FreeImage is disguised as ImageFactory.

 

The bits go to a GLBitmap Constructor ( .. bmp->GetPixel(x, y) ), along with width, height, and whether the bits need shuffling or not when they get copied.

 

The GLBitmap goes to a GLTexture, which takes the width and height and the bits and does the OpenGL stuff in GLTexture::Load. 


Cream::GLTexture Cream::LoadTexture(std::string path)
{
ImageFactory* factory = ImageFactory::Create();
 
unsigned int width(0), height(0);
bool bShuffle(false);
 
BYTE* bits = factory->Load( path, width, height, bShuffle );
 
GLBitmap* bitmap = new GLBitmap( width, height, bShuffle, bits );
 
GLTexture texture(GL_TEXTURE_2D, GL_RGBA);
 
texture.SetParam(GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
texture.SetParam(GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
texture.SetParam(GL_TEXTURE_MIN_FILTER, GL_LINEAR);
texture.SetParam(GL_TEXTURE_MAG_FILTER, GL_LINEAR);
 
texture.Load( bitmap );
 
return texture;
}

Okay, so here's the constructor for GLBitmap - a Pixel is 4 bytes, a BYTE is an unsigned char. You knew that. So we cast the bits to Pixels and we know we have w * h of them. This could be a place where things have gone wrong though.

GLBitmap(int w, int h, bool bShuffle, BYTE* bits)
{
	width = w;
	height = h;
	Pixel* src = (Pixel*)bits;

	pixels = new Pixel[w*h];

	for(int i = 0; i < w; ++i)
	{
		for(int j = 0 ; j < h; ++j)
		{			
			const Pixel& p = src[(i * h) + j];
			pixels[(i * h) + j] = (bShuffle) ? Pixel(p.B, p.G, p.R, p.A) : p ;
		}
	}
}

And finally our wrapper for an int, GLTexture, here's the Load method, that makes the actual OpenGL calls to generate a texture ID and set the bits to it.

bool GLTexture::Load( GLBitmap* bitmap )
{
	glGenTextures( 1, &m_GLID );
	glBindTexture( target, m_GLID );

	glTexImage2D( target, 0, GL_RGBA, bitmap->Width(), bitmap->Height(), 
                              0, GL_BGRA, GL_UNSIGNED_BYTE, bitmap->Data() );

	for( auto i = params.begin(); i != params.end(); ++i )
	        glTexParameteri( target, i->first, i->second );
 
	return (m_GLID!=0);
}

And so, that explains, in SetMaterial, the workings behind Cream::LoadTexture()

if(mat->isTextured)
{
	material->isTextured = true;

	if(mat->mapKd.size() != 0)	// if there is a filename
	{
		if(mat->KdID != 0)		//if there is a gl/sl tex unit id
			material->KdID = mat->KdID;	//grab it
		else
		{
			m_Textures[0] = Cream::LoadTexture( mat->mapKd ); // else load it
			material->KdID = m_Textures[0].ID();
		}
		material->mapKd = mat->mapKd;
	}
....

So where's my error.. Well I suspect a couple of things. I have a debug callback set, would it inform me of anything obvious?

- the glActiveTexture(GLTEXTURE0+n) calls - they're wrong - the wrong place, too often, wrong texture unit ?
- not sending the right value through to the sampler in the shader*, and no map is being sampled.. linked to above?
- the bits were mangled or the pointer lost by the time OpenGL gets to them in GLTexture::Load

As I say, the coloured phong shader and the textured phong shader are identical except for swapping a vec4 uniform for a sampler and a vec2 attribute, and getting the colour by sampling the texture.

Everything renders fine except the textured-not-coloured stuff.

Please find my error(s), I'll be around to let you know how much you helped! It was a long post.. apologies! A lot of code..

Thank you so, so much in advance! There's a lot I want to do with textures that I can't yet!

In fact, here's a screenshot of a mildly shiny blue cube, a white floor-grid, and a square black hole. I kid, it's that quad.

 

 

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Is your quad rendered with the shader on? Are you able to output a debug red color to verify the shader is on?

Are you binding the texture and sending the uniform to the shader?

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Screenshots up. See the cube and the black quad? I can render that quad using that cube's shader and get a nice yellow on it. I simply set material->isTextured to false and give the other shader names in the GLMesh constructor way at the top. And set a colour on the material.

Okay.. the generic colured shader gives me yellow, the phong shader on the quad makes it black, same phong shader as the cube.. curiouser and curiouser..!
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Could you explain what "Everything renders fine except the textured-not-coloured stuff." means? maybe a screenshot?


If I use texture shader, black. If coloured shader, fine. I say 'stuff' because I think the issue with the texturing resides in the texture stuff.. GLTexture, GLBitmap, or setting the texture / binding it. glGenTextures gives me a texture id, even when I was giving it nothing cos I had been calling FreeImage_Unload too early.. 80% sure that those are the right bytes going on the card. Lol.
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So do any of your models/shaders have a textured model? Are you sending the uniform to the shader? What does your shader look like?

Does the quad have normal? Can you at least strip your shader down to texture2D(diffuse, texCoord))...... don't know if its a lighting problem/attribute problem, uniform problem, bad texture problem..

Why don't you verify glUseProgram(0) and binding the texture shows up on your quad wihtout using a shader.

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So do any of your models/shaders have a textured model? Are you sending the uniform to the shader? What does your shader look like?
Does the quad have normal? Can you at least strip your shader down to texture2D(diffuse, texCoord))...... don't know if its a lighting problem/attribute problem, uniform problem, bad texture problem..
Why don't you verify glUseProgram(0) and binding the texture shows up on your quad wihtout using a shader.


1. What?
2. Yes. All the lighting colours vectors, a bunch of matrices, and the texture unit all go to the shader no problem. The GLMesh looks at the material in SetMaterial(), checking for a gl tex id or texture path, and loads texture via a factory (Freeimage) if it needs to. In GLMesh::Render, GLMesh::PreRenderlooks at the material it holds and sets a colour if there is no texture ids - PreRender sets uniforms. See the code in the original post.

3. Look like? There is a basic coloured pass thru shader, a phong coloured shader, and a phong textured shader. In the screenshot in the original post, the phong coloured is the cube on the right, the coloured pass thru is the XYZ and the grid, and the textured quad shader is the black quad in the middle.

I rendered the quad with the pass thru shader, uniform colour as yellow, and it was yellow. I use the textured phong shader or the coloured phong shader, and the quad is black. Verr strange.

As shown in the code in the original post, the quad has four vertices and four normals, each normal is z positive.

The phong colour and phong texture shader are identical except the change from a uniform vec4 colour to a in vec2 uv and a uniform sampler2D tex.
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What happens if you use these tex coords

 

shape->m_TexCoords[0] = Vertex2D(1.0f, 0.0f);
shape->m_TexCoords[1] = Vertex2D(0.0f, 0.0f);
shape->m_TexCoords[2] = Vertex2D(0.0f, 1.0f);
shape->m_TexCoords[3] = Vertex2D(1.0f, 1.0f);

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Sorry I disappeared - work/sleep.
 

 

What happens if you use these tex coords

 

shape->m_TexCoords[0] = Vertex2D(1.0f, 0.0f);
shape->m_TexCoords[1] = Vertex2D(0.0f, 0.0f);
shape->m_TexCoords[2] = Vertex2D(0.0f, 1.0f);
shape->m_TexCoords[3] = Vertex2D(1.0f, 1.0f);

 

Trying them now..

Legen..  You are SO AWESOME, THANKYOU!

Seriously for chewing through that first post and it was just the texture coordinates.. I'm glad though, that it was a noob error and not down to the whole mechanism of materials, geometry, vaos n shaders, and those texture classes.. there's some saving face in that, I think.

I'll let you in on a secret: I changed my phong shader fragment shader to just set fragColour as what it sampled, no lighting calcs.. something may be wrong with my normals or the phong code.. another thread, coming soon *facepalm*.

Thank you again! So was my texture' backwards' or 'inside out' or what?

..-dary!
 

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From the original post you seem to have specified the quad verts as botRight -> botLeft -> topLeft -> topRight, but the quad texcoords were

topLeft -> topRight -> botRight -> botLeft so the order didnt match.

Edited by NumberXaero
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Next step, get an importer/exporter system for 3D models instead of programmatically making geometry. Should be first thing on your todo list.

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From the original post you seem to have specified the quad verts as botRight -> botLeft -> topLeft -> topRight, but the quad texcoords were

topLeft -> topRight -> botRight -> botLeft so the order didnt match.

This is exactly my problem! I've been doing some testing with my 3 shaders.

- The basic coloured one always works on models and on the quad.
- The coloured phong shader on models works (does it..?) - the models appear blue and shiny, like the cube there. But it doesn't work on my quad - until
- The textured phong shader works on the quad - when I set all the normals to (0.0, 0.0 -1.0) - so does the coloured phong shader.

I haven't tried a texture on a mesh.. though obviously I want to. So my quad is wound all wrong! And my texturing stuff works.

So what order is the most used or correct way to wind a quad? I'm always worrying about triangles recently.

I would imagine it should be top right, bottom right, top left, bottom left? Or do you do them counter/clockwise, like a tri, - something like bottom right, top right, top left, bottom left? I'm guessing this is important for rendering meshes that are quads?

Using your texture coordinates, and making x0 negative and x1 positive, y0 negative and y1 positive (that was poor mistake I admit), and setting my normals to -Z, I get this with the textured phong shader. Is my Quad wound the wrong way?


 

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Winding and texture coord order is important for everything, I use CCW = front, but it doesnt matter you just have to make sure its consistent with your cull winding.

If your vertex winding is not what you intended then your triangles will have their front faces culled when backface culling is enabled. You see this in poorly created models that have missing triangles when view from the outside, its because the winding on all the triangle is not consistent

If your texture coordinates dont fall where they should your texture might be distored, flipped horzontally or vertically. With textures like rocks with no obvious up/down left/right it can make it difficult to notice these problems. Make a basic texture for testing. Say with a capital L on the left of the image, colored red, T at top for top another color, Bottom, Right, etc. Give it a 1 pixel border, place a circle dead center. This will help you notice flips, stretches, and tiling better. Use a white background so you can notice any strange color changes.

 

Im not sure if what Im seeing is wrong, because If have no way to gauge if that texture looks wrong or not, Its features dont say right or wrong.

Edited by NumberXaero
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I know about winding in general, I guess I meant which corner do I start from? - I am using GL_QUADS.

Im going to check my culling settings, pretty sure I'm using using counter clockwise and culling back faces.. Ill edit this post when I find out, just cooking

PS that texture has some text on it, its just a random sample.
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      #include "MyFileHandler.h" MyFileHandler::MyFileHandler(const char * fileName) { this->fileName = fileName; this->setFileSize(); } MyFileHandler::~MyFileHandler() { } void MyFileHandler::setFileSize() { FILE * fileHandle = NULL; fopen_s(&fileHandle, this->fileName, "rb"); fseek(fileHandle, 0L, SEEK_END); this->fileSize = ftell(fileHandle); rewind(fileHandle); fclose(fileHandle); return; } unsigned long MyFileHandler::getFileSize() { return (this->fileSize); } const char * MyFileHandler::readFile() { char * buffer = (char *)malloc((this->fileSize)+1); FILE * fileHandle = NULL; fopen_s(&fileHandle, this->fileName, "rb"); fread(buffer, this->fileSize, sizeof(char), fileHandle); fclose(fileHandle); buffer[this->fileSize] = '\0'; return buffer; } VertexShader.glsl
      #version 330 core layout (location = 0) vec3 VertexPositions; void main() { gl_Position = vec4(VertexPositions, 1.0f); } FragmentShader.glsl
      #version 330 core out vec4 FragmentColor; void main() { FragmentColor = vec4(1.0f, 0.0f, 0.0f, 1.0f); } I am attempting to create a simple engine/graphics utility using some object-oriented paradigms. My first goal is to get some output from my engine, namely, a simple red triangle.
      For this goal, the MyShapes class will be responsible for defining shapes such as triangles, polygons etc. Currently, there is only a drawTriangle() method implemented, because I first wanted to see whether it works or not before attempting to code other shape drawing methods.
      The constructor of the MyEngine class creates a GLFW window (GLAD is also initialized here to load all OpenGL functionality), and the myEngine.run() method in Main.cpp is responsible for firing up the engine. In this run() method, the shaders get loaded from files via the help of my FileHandler class. The vertices for the triangle are processed by the myShapes.drawTriangle() method where a vertex array object, a vertex buffer object and vertrex attributes are set for this purpose.
      The while loop in the run() method should be outputting me the desired red triangle, but all I get is a grey window area. Why?
      Note: The shaders are compiling and linking without any errors.
      (Note: I am aware that this code is not using any good software engineering practices (e.g. exceptions, error handling). I am planning to implement them later, once I get the hang of OpenGL.)

       
    • By KarimIO
      EDIT: I thought this was restricted to Attribute-Created GL contexts, but it isn't, so I rewrote the post.
      Hey guys, whenever I call SwapBuffers(hDC), I get a crash, and I get a "Too many posts were made to a semaphore." from Windows as I call SwapBuffers. What could be the cause of this?
      Update: No crash occurs if I don't draw, just clear and swap.
      static PIXELFORMATDESCRIPTOR pfd = // pfd Tells Windows How We Want Things To Be { sizeof(PIXELFORMATDESCRIPTOR), // Size Of This Pixel Format Descriptor 1, // Version Number PFD_DRAW_TO_WINDOW | // Format Must Support Window PFD_SUPPORT_OPENGL | // Format Must Support OpenGL PFD_DOUBLEBUFFER, // Must Support Double Buffering PFD_TYPE_RGBA, // Request An RGBA Format 32, // Select Our Color Depth 0, 0, 0, 0, 0, 0, // Color Bits Ignored 0, // No Alpha Buffer 0, // Shift Bit Ignored 0, // No Accumulation Buffer 0, 0, 0, 0, // Accumulation Bits Ignored 24, // 24Bit Z-Buffer (Depth Buffer) 0, // No Stencil Buffer 0, // No Auxiliary Buffer PFD_MAIN_PLANE, // Main Drawing Layer 0, // Reserved 0, 0, 0 // Layer Masks Ignored }; if (!(hDC = GetDC(windowHandle))) return false; unsigned int PixelFormat; if (!(PixelFormat = ChoosePixelFormat(hDC, &pfd))) return false; if (!SetPixelFormat(hDC, PixelFormat, &pfd)) return false; hRC = wglCreateContext(hDC); if (!hRC) { std::cout << "wglCreateContext Failed!\n"; return false; } if (wglMakeCurrent(hDC, hRC) == NULL) { std::cout << "Make Context Current Second Failed!\n"; return false; } ... // OGL Buffer Initialization glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT); glBindVertexArray(vao); glUseProgram(myprogram); glDrawElements(GL_TRIANGLES, indexCount, GL_UNSIGNED_SHORT, (void *)indexStart); SwapBuffers(GetDC(window_handle));  
    • By Tchom
      Hey devs!
       
      I've been working on a OpenGL ES 2.0 android engine and I have begun implementing some simple (point) lighting. I had something fairly simple working, so I tried to get fancy and added color-tinting light. And it works great... with only one or two lights. Any more than that, the application drops about 15 frames per light added (my ideal is at least 4 or 5). I know implementing lighting is expensive, I just didn't think it was that expensive. I'm fairly new to the world of OpenGL and GLSL, so there is a good chance I've written some crappy shader code. If anyone had any feedback or tips on how I can optimize this code, please let me know.
       
      Vertex Shader
      uniform mat4 u_MVPMatrix; uniform mat4 u_MVMatrix; attribute vec4 a_Position; attribute vec3 a_Normal; attribute vec2 a_TexCoordinate; varying vec3 v_Position; varying vec3 v_Normal; varying vec2 v_TexCoordinate; void main() { v_Position = vec3(u_MVMatrix * a_Position); v_TexCoordinate = a_TexCoordinate; v_Normal = vec3(u_MVMatrix * vec4(a_Normal, 0.0)); gl_Position = u_MVPMatrix * a_Position; } Fragment Shader
      precision mediump float; uniform vec4 u_LightPos["+numLights+"]; uniform vec4 u_LightColours["+numLights+"]; uniform float u_LightPower["+numLights+"]; uniform sampler2D u_Texture; varying vec3 v_Position; varying vec3 v_Normal; varying vec2 v_TexCoordinate; void main() { gl_FragColor = (texture2D(u_Texture, v_TexCoordinate)); float diffuse = 0.0; vec4 colourSum = vec4(1.0); for (int i = 0; i < "+numLights+"; i++) { vec3 toPointLight = vec3(u_LightPos[i]); float distance = length(toPointLight - v_Position); vec3 lightVector = normalize(toPointLight - v_Position); float diffuseDiff = 0.0; // The diffuse difference contributed from current light diffuseDiff = max(dot(v_Normal, lightVector), 0.0); diffuseDiff = diffuseDiff * (1.0 / (1.0 + ((1.0-u_LightPower[i])* distance * distance))); //Determine attenuatio diffuse += diffuseDiff; gl_FragColor.rgb *= vec3(1.0) / ((vec3(1.0) + ((vec3(1.0) - vec3(u_LightColours[i]))*diffuseDiff))); //The expensive part } diffuse += 0.1; //Add ambient light gl_FragColor.rgb *= diffuse; } Am I making any rookie mistakes? Or am I just being unrealistic about what I can do? Thanks in advance
    • By yahiko00
      Hi,
      Not sure to post at the right place, if not, please forgive me...
      For a game project I am working on, I would like to implement a 2D starfield as a background.
      I do not want to deal with static tiles, since I plan to slowly animate the starfield. So, I am trying to figure out how to generate a random starfield for the entire map.
      I feel that using a uniform distribution for the stars will not do the trick. Instead I would like something similar to the screenshot below, taken from the game Star Wars: Empire At War (all credits to Lucasfilm, Disney, and so on...).

      Is there someone who could have an idea of a distribution which could result in such a starfield?
      Any insight would be appreciated
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