Sign in to follow this  
Followers 0
ScherzkeCks

OpenGL
[Solved]Can't render Text

12 posts in this topic

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
0

Share this post


Link to post
Share on other sites

Print the coordinates of the vertices you are putting into the vertex buffer.  Ensure they are neither too small nor too large.

Disable culling.  Disable depth testing.

 

 

L. Spiro

1

Share this post


Link to post
Share on other sites

I did print the coordinates and made all the math on them by hand. and while certainly a little large for text they all are within the window.

Culling and Depth testing also disabled but no difference. 

0

Share this post


Link to post
Share on other sites

First letter:

 

v1: x:125.000000 y:148.000000 

v2: x:137.000000 y:148.000000 

v3: x:125.000000 y:170.000000 

v4: x:137.000000 y:170.000000 

0

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
0

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. 

0

Share this post


Link to post
Share on other sites

Well I am down to just glClear() the TextDrawing code and the buffer swapping. Also the vertex-Shader only outputs white now. Still only a black screen.

0

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;
}
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. 

0

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.

0

Share this post


Link to post
Share on other sites

I believe VAO was made mandatory in OpenGL 4.0 or thereabout. In any case, yes, it is mandatory to use VAO in later versions at least.

0

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  
Followers 0

  • Similar Content

    • By recp
      Hi,
      I'm working on new asset importer (https://github.com/recp/assetkit) based on COLLADA specs, the question is not about COLLADA directly
      also I'm working on a new renderer to render (https://github.com/recp/libgk) imported document.
      In the future I'll spend more time on this renderer of course, currently rendering imported (implemented parts) is enough for me
      assetkit imports COLLADA document (it will support glTF too),
      importing scene, geometries, effects/materials, 2d textures and rendering them seems working
      My actual confusion is about shaders. COLLADA has COMMON profile and GLSL... profiles,
      GLSL profile provides shaders for effects so I don't need to wory about them just compile, link, group them before render

      The problem occours in COMMON profile because I need to write shaders,
      Actually I wrote them for basic matrials and another version for 2d texture
      I would like to create multiple program but I am not sure how to split this this shader into smaller ones,

      Basic material version (only colors):
      https://github.com/recp/libgk/blob/master/src/default/shader/gk_default.frag
      Texture version:
      https://gist.github.com/recp/b0368c74c35d9d6912f524624bfbf5a3
      I used subroutines to bind materials, actually I liked it,
      In scene graph every node can have different program, and it switches between them if parentNode->program != node->program
      (I'll do scene graph optimizations e.g.  view frustum culling, grouping shaders... later)

      I'm going to implement transparency but I'm considering to create separate shaders,
      because default shader is going to be branching hell
      I can't generate shader for every node because I don't know how many node can be exist, there is no limit.
      I don't know how to write a good uber-shader for different cases:

      Here material struct:
      struct Material { ColorOrTexture emission; ColorOrTexture ambient; ColorOrTexture specular; ColorOrTexture reflective; ColorOrTexture transparent; ColorOrTexture diffuse; float shininess; float reflectivEyety; float transparency; float indexOfRefraction; }; ColorOrTexture could be color or 2d texture, if there would be single colorOrTex then I could split into two programs,
      Also I'm going to implement transparency, I am not sure how many program that I needed

      I'm considering to maintain a few default shaders for COMMON profile,
      1-no-texture, 2-one of colorOrTexture contains texture, 3-........

      Any advices in general or about how to optimize/split (if I need) these shaders which I provied as link?
      What do you think the shaders I wrote, I would like to write them without branching if posible,
      I hope I don't need to write 50+ or 100+ shaders, and 100+ default programs

      PS: These default shaders should render any document, they are not specific, they are general purpose...
             I'm compiling and linking default shaders when app launched

      Thanks
    • By CircleOfLight97
      Hi guys,
      I would like to contribute to a game project as a developer (open source possibly). I have some experiences in C/C++ in game development (perso projects). I don't know either unreal or unity but I have some knowledges in opengl, glsl and shading theory as I had some courses at university regarding to that. I have some knowledges in maths and basic in physics. I know a little how to use blender to do modelling, texturing and simple game assets (no characters, no animation no skinning/rigging). I have no game preferences but I like aventure game, dungeon crawler, platformers, randomly generated things. I know these kind of projects involve a lot of time and I'd be really to work on it but if there are no cleary defined specific design goals/stories/gameplay mechanics I would like to not be part of it x) and I would rather prefer a smaller but well defined project to work on that a huge and not 'finishable' one.
      CircleOfLight97
    • By gamesthatcouldbeworse
      Hi, I finally released KILL COMMANDO on gamejolt for free. It is a retro-funsplatter-shooter with C64 style. Give it a try.
    • By phil67rpg

      void TimerFunction(int value) {  glutPostRedisplay();  glutTimerFunc(1000, TimerFunction, 1); } void drawScene() {  glClear(GL_COLOR_BUFFER_BIT);      drawScene_bug();  TimerFunction(1);  eraseScene_bug(); // drawScene_bug_two(); // eraseScene_bug_two(); drawScene_ship(); drawScene_bullet();  glutSwapBuffers(); }
  • Popular Now