Sign in to follow this  
ScherzkeCks

OpenGL [Solved]Can't render Text

Recommended Posts

Hi everybody,

 

I have been staring at this code for 3 days now and rewritten it 2 times with no effect. I know, that the texture and the shaders get loaded just fine (confirmed that using OpenGL Profiler on Mac). The shaders work as tested with my normal draws. But the function posted below doesn't put out anything. All the values in the vectors supplied to OpenGL are fine as well. I also tried using simple arrays instead of vectors(which shouldn't make a difference) to no avail. Can somebody tell me what it is?

bool Text::drawText(int x, int y, std::string text) {
	if (programID == 0)
	{
		return false;
	}
	if (textureID == 0)
	{
		return false;
	}

	int xOffset = 0;
    std::vector<glm::vec2> vertices;
    std::vector<glm::vec2> uvCoordinats;
	for (int i = 0; i < text.size(); ++i)
	{
		int id = text[i];
		for (int j = 0; j < glyphCount; ++j)
		{
			if (glyphs[j].id == id)
			{
				/**
				 * calculate vertices and stuff
				 * Layout is as follows:
				 *     v1    v2
				 *     ------
				 *     |  / |
				 *     | /  |
				 *     ------
				 *     v3    4
				 */
                
                
                glm::vec2 v1 = glm::vec2(x + xOffset + glyphs[j].xoffset, y + glyphs[j].yoffset);
                glm::vec2 v2 = glm::vec2(x + xOffset + glyphs[j].xoffset + glyphs[j].width, y + glyphs[j].yoffset);
                glm::vec2 v3 = glm::vec2(x + xOffset + glyphs[j].xoffset,y + glyphs[j].yoffset + glyphs[j].height);
                glm::vec2 v4 = glm::vec2(x + xOffset + glyphs[j].xoffset + glyphs[j].width, y + glyphs[j].yoffset + glyphs[j].height);
                
                vertices.push_back(v1);
                vertices.push_back(v2);
                vertices.push_back(v3);
                
                vertices.push_back(v3);
                vertices.push_back(v2);
                vertices.push_back(v4);
                
                glm::vec2 uv1 = glm::vec2((GLfloat)(glyphs[j].x)/ textureWidth, (GLfloat)(glyphs[j].y) / textureHeight);
                glm::vec2 uv2 = glm::vec2((GLfloat)(glyphs[j].x + glyphs[j].width) / textureWidth,(GLfloat)(glyphs[j].y) / textureHeight);
                glm::vec2 uv3 = glm::vec2((GLfloat)(glyphs[j].x) /textureWidth,(GLfloat)(glyphs[j].y + glyphs[j].height) /textureHeight);
                glm::vec2 uv4 = glm::vec2((GLfloat)(glyphs[j].x + glyphs[j].width) / textureWidth,(GLfloat)(glyphs[j].y + glyphs[j].height) /textureHeight);
                
                
                uvCoordinats.push_back(uv1);
                uvCoordinats.push_back(uv2);
                uvCoordinats.push_back(uv3);
                
                uvCoordinats.push_back(uv3);
                uvCoordinats.push_back(uv2);
                uvCoordinats.push_back(uv4);

                xOffset += glyphs[j].advance;
				break;
			}
		}
	}
    
    //time to draw
    glUseProgram(programID);
    
    glBindVertexArray(0);
    
    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, textureID);
    GLuint textureSampler = glGetUniformLocation(programID,"myTextureSampler");
    glUniform1i(textureSampler,0);
    
    
    GLuint buffers[2];
    glGenBuffers(2,buffers);
    
    glEnableVertexAttribArray(RENDER_POSITION_LOCATION);
    glBindBuffer(GL_ARRAY_BUFFER,buffers[0]);
    glBufferData(GL_ARRAY_BUFFER,vertices.size() * sizeof(glm::vec2),&vertices[0],GL_STATIC_DRAW);
    glVertexAttribPointer(RENDER_POSITION_LOCATION,2,GL_FLOAT,GL_FALSE,0,0);
    
    glEnableVertexAttribArray(RENDER_UV_LOCATION);
    glBindBuffer(GL_ARRAY_BUFFER,buffers[1]);
    glBufferData(GL_ARRAY_BUFFER,uvCoordinats.size() * sizeof(glm::vec2),&uvCoordinats[0],GL_STATIC_DRAW);
    glVertexAttribPointer(RENDER_UV_LOCATION,2,GL_FLOAT,GL_FALSE,0,0);
    
    
    glDrawArrays(GL_TRIANGLES, 0, (GLint)vertices.size());
    
    glDeleteBuffers(2,buffers);
    glBindTexture(GL_TEXTURE_2D,0);

	return true;
}

And the Shaders for the sake of it:

Vertex:

#version 150
in vec2 in_Position;
in vec2 in_UV;

out vec2 ex_UV;

void main(void)
{
    //Position is in a Range of [0,500]*[0,500] and has to be mapped to [-1,1]*[-1,1]
    vec2 out_Position = in_Position - vec2(250,250);
    out_Position = out_Position / vec2(250,250);
	gl_Position = vec4(out_Position,0,1);
	ex_UV = in_UV;
}

Fragment:

#version 150
in vec2 ex_UV;

out vec4 out_Color;

uniform sampler2D myTextureSampler;

void main(void)
{
	out_Color = texture(myTextureSampler, ex_UV);
}
Edited by ScherzkeCks

Share this post


Link to post
Share on other sites

tried both, nothing changed.

 

Could it be some kind of wrong calls to change states? I will post the only other part of code that makes opengl calls after the creation of the window, maybe I am doing something wrong when switching from Model-Drawing to Text-Drawing.

 

This code gets called right before i call the drawText() function (This part works just fine)

void Render::renderObjects()
{

	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	glUseProgram(programID);

	//Texture-Sampler Location
	GLuint textureSampler = glGetUniformLocation(programID,"myTextureSampler");

	GLint vpLocation = glGetUniformLocation(programID,"VP");
	glm::mat4 vp = GameManager::getSingleton()->getCamera()->getCameraMatrix();
	glUniformMatrix4fv(vpLocation,1,GL_FALSE,&vp[0][0]);

	GLint modelMatrixLocation = glGetUniformLocation(programID,"model");

	std::vector<RenderObject *> objectsToRender;

	objectsToRender = GameManager::getSingleton()->getROManager()->getObjectsToRender();



	for (int i = 0; i < objectsToRender.size(); ++i)
	{
		RenderObject *currentObject = objectsToRender.at(i);
		GLuint vertexArrayObjectName = currentObject->getVertexArrayName();
		if (vertexArrayObjectName == 0)
		{
			//Create vertexarrayobject and buffers etc.
			GLfloat* vertices = NULL;
			GLfloat* normals = NULL;
			GLuint* indices = NULL;
			GLfloat* uvCoordinates = NULL;
			int verticesCount;
			int indicesCount;
			short textureWidth, textureHeight;
			char* textureData = NULL;
			try {
				currentObject->getData(&vertices, &normals, &indices, &uvCoordinates, &verticesCount, &indicesCount, &textureWidth, &textureHeight, &textureData);
			}
			catch (RenderObjectException* e) {
				printf("%s\n", e->what());
				//TODO: remove from objectHandler and further error-Handling
				continue;
			}

			//Texture
			GLuint textureID;
			glGenTextures(1, &textureID);
			glBindTexture(GL_TEXTURE_2D, textureID);
			//glTexStorage2D(GL_TEXTURE_2D,4, GL_RGB, textureWidth, textureHeight);
			//glTexSubImage2D(GL_TEXTURE_2D,0,0,0,textureWidth,textureHeight,GL_BGR, GL_UNSIGNED_BYTE, textureData);
			glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, textureWidth, textureHeight, 0, GL_BGR, GL_UNSIGNED_BYTE, textureData); // <- tutorial version but mutable

			glGenerateMipmap(GL_TEXTURE_2D);

			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR_MIPMAP_NEAREST);
			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
			//glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT );
			//glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT );

			currentObject->setTextureID(textureID);

			//creating vertexarray
			glGenVertexArrays(1,&vertexArrayObjectName);
			glBindVertexArray(vertexArrayObjectName);

			currentObject->setVertexArrayName(vertexArrayObjectName);

			//create the buffers belonging to this vertexarray
			GLuint vboId;
			glGenBuffers(1,&vboId);
			glBindBuffer(GL_ARRAY_BUFFER,vboId);
			glBufferData(GL_ARRAY_BUFFER,verticesCount * sizeof(GLfloat) * 4,vertices, GL_STATIC_DRAW);
			glVertexAttribPointer(RENDER_POSITION_LOCATION,4,GL_FLOAT,GL_FALSE,0,0);
			glEnableVertexAttribArray(RENDER_POSITION_LOCATION);

			//normalBuffer
			GLuint normalBuffer;
			glGenBuffers(1,&normalBuffer);
			glBindBuffer(GL_ARRAY_BUFFER,normalBuffer);
			glBufferData(GL_ARRAY_BUFFER, verticesCount * 4 * sizeof(GLfloat),normals, GL_STATIC_DRAW);
			glVertexAttribPointer(RENDER_NORMALS_LOCATION,4,GL_FLOAT,GL_FALSE,0,NULL);
			glEnableVertexAttribArray(RENDER_NORMALS_LOCATION);

			//uvCoordinatesBuffer
			GLuint uvCoordinatesID;
			glGenBuffers(1,&uvCoordinatesID);
			glBindBuffer(GL_ARRAY_BUFFER,uvCoordinatesID);
			glBufferData(GL_ARRAY_BUFFER,verticesCount * sizeof(GLfloat) * 2,uvCoordinates,GL_STATIC_DRAW);
			glVertexAttribPointer(RENDER_UV_LOCATION,2,GL_FLOAT,GL_FALSE,0,0);
			glEnableVertexAttribArray(RENDER_UV_LOCATION);

			GLuint indicesID;
			glGenBuffers(1,&indicesID);
			glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,indicesID);
			glBufferData(GL_ELEMENT_ARRAY_BUFFER,indicesCount * sizeof(GLuint),indices,GL_STATIC_DRAW);

			glBindVertexArray(0);


		}


		glActiveTexture(GL_TEXTURE0);
		glBindTexture(GL_TEXTURE_2D, currentObject->getTextureID());
		glUniform1i(textureSampler,0);

		glm::mat4  modelMatrix = currentObject->getModelMatrix();

		glUniformMatrix4fv(modelMatrixLocation,1,GL_FALSE,&modelMatrix[0][0]);

		glBindVertexArray(vertexArrayObjectName);

		glDrawElements(GL_TRIANGLES,currentObject->getIndicesCount(),GL_UNSIGNED_INT,0);

		glBindVertexArray(0);
		

	}
	
}

Edited by ScherzkeCks

Share this post


Link to post
Share on other sites

Have you tried replacing the fragment shader by writing out just white, just to make sure that the texture coordinates are not wrong? I would suggest you make the code as minimal as possible, I think that is the best way to find out this kind of bugs. Comment out all unnecessary stuff, render the text and do nothing else and see if that works. 

Share this post


Link to post
Share on other sites

Had to try it myself, the code you have shown seems ok. This draws pink quads for the characters:

// g++ -std=c++11 text.cpp $(pkg-config --libs --cflags sdl glew) && ./a.out
#include <iostream>
#include <vector>

#include "SDL.h"
#include <GL/glew.h>
#include <glm/glm.hpp>

unsigned int program;

const char *vs_source = 
"#version 150\n"
"in vec2 in_Position;\n"
"void main(void) {\n"
"    //Position is in a Range of [0,500]*[0,500] and has to be mapped to [-1,1]*[-1,1]\n"
"    vec2 out_Position = in_Position - vec2(250);\n"
"    out_Position = out_Position / vec2(250);\n"
"    gl_Position = vec4(out_Position,0,1);\n"
"}\n";

const char *fs_source = 
"#version 150\n"
"out vec4 out_Color;\n"
"void main(void) {\n"
"    out_Color = vec4(1,0,1,1);\n"
"}\n";

unsigned int program_create() {
    GLuint p = glCreateProgram();
    GLuint vs = glCreateShader(GL_VERTEX_SHADER);
    GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);

    glShaderSource(vs, 1, &vs_source, 0);
    glAttachShader(p, vs);
    glCompileShader(vs);

    glShaderSource(fs, 1, &fs_source, 0);
    glCompileShader(fs);
    glAttachShader(p, fs);

    glBindAttribLocation(p, 0, "in_Position");

    glLinkProgram(p);

    return p;
}

bool drawText(int x, int y, const std::string &text) {
    std::vector<glm::vec2> vertices;

    float offsetx = x;
    float offsety = y;
    for(size_t i=0; i<text.size(); ++i) {
        glm::vec2 v1 = glm::vec2(offsetx, offsety);
        glm::vec2 v2 = glm::vec2(offsetx+10, offsety);
        glm::vec2 v3 = glm::vec2(offsetx, offsety+20);
        glm::vec2 v4 = glm::vec2(offsetx+10, offsety+20);
        vertices.push_back(v1);
        vertices.push_back(v2);
        vertices.push_back(v3);
        vertices.push_back(v3);
        vertices.push_back(v2);
        vertices.push_back(v4);
       offsetx += 15;
    }

    glUseProgram(program);

    GLuint vbo;
    glGenBuffers(1, &vbo);

    glEnableVertexAttribArray(0);
    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glBufferData(GL_ARRAY_BUFFER, vertices.size() * sizeof(glm::vec2), &vertices[0], GL_STATIC_DRAW);
    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE,0,0);

    glDrawArrays(GL_TRIANGLES, 0, (GLint)vertices.size());

    glDeleteBuffers(1, &vbo);
    glBindTexture(GL_TEXTURE_2D,0);

    return true;
}

int main(int argc, char **argv) {
    bool running = true;

    SDL_Init(SDL_INIT_EVERYTHING);
    SDL_SetVideoMode(1280, 800, 0, SDL_OPENGL);

    glewInit();

    program = program_create();

    SDL_Event event;
    while(running) {
        while(SDL_PollEvent(&event)) {
            switch(event.type) {
                case SDL_QUIT: running = false; break;
                case SDL_KEYDOWN: running = !(event.key.keysym.sym == SDLK_ESCAPE); break;
            }
        }
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        drawText(250, 250, "hello");
        SDL_GL_SwapBuffers();
        assert(glGetError() == GL_NO_ERROR);
    }

    SDL_Quit();
    return 0;
}

Share this post


Link to post
Share on other sites

Yeah, but then it has to be something in between that code and the objectdrawing code which works too.

 

But I am not doing anything in between other than what is written in the code above. The drawText method gets called literally right after the renderObjects() call. 

But even if I just call the drawText() code it doesn't work

 

Just for your information, I am using GLFW instead of SDL but that shouldn't matter as far as I can tell. 

Share this post


Link to post
Share on other sites

Alright, I solved it. And because somebody might search this in the future I will post the solution here:

 

I had to use a VertexArrayObject for the text, then it would draw just fine.

 

I was under the impression, that you don't have to use VAOs but I guess I was wrong.

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
      628368
    • Total Posts
      2982293
  • Similar Content

    • By test opty
      Hi all,
       
      I'm starting OpenGL using a tut on the Web. But at this point I would like to know the primitives needed for creating a window using OpenGL. So on Windows and using MS VS 2017, what is the simplest code required to render a window with the title of "First Rectangle", please?
       
       
    • By DejayHextrix
      Hi, New here. 
      I need some help. My fiance and I like to play this mobile game online that goes by real time. Her and I are always working but when we have free time we like to play this game. We don't always got time throughout the day to Queue Buildings, troops, Upgrades....etc.... 
      I was told to look into DLL Injection and OpenGL/DirectX Hooking. Is this true? Is this what I need to learn? 
      How do I read the Android files, or modify the files, or get the in-game tags/variables for the game I want? 
      Any assistance on this would be most appreciated. I been everywhere and seems no one knows or is to lazy to help me out. It would be nice to have assistance for once. I don't know what I need to learn. 
      So links of topics I need to learn within the comment section would be SOOOOO.....Helpful. Anything to just get me started. 
      Thanks, 
      Dejay Hextrix 
    • 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.
  • Popular Now