[Solved]Can't render Text

Stefan R · 2013-09-30T21:33:45

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); }

Graphics and GPU Programming Programming OpenGL

Started by ScherzkeCks September 19, 2013 04:38 PM

11 comments, last by Brother Bob 10 years, 6 months ago

ScherzkeCks

117

Author

September 24, 2013 09:57 PM

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.

ScherzkeCks

117

Author

September 30, 2013 09:08 PM

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.

Brother Bob

10,350

September 30, 2013 09:33 PM

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.

[Solved]Can't render Text

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[Solved]Can't render Text

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