• Advertisement
Sign in to follow this  

OpenGL How to rendering fast bitmap fonts/text

This topic is 1278 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Hi there,

i have implemented signed distance field bitmap fonts creation and rendering successfully in a simple opengl sample.
The rendering is a mix of modern shader stuff and immediate mode for translating and scaling the characters, but this are not allowed in my actual game engine. Only opengl es 2.0 compatible rendering is allowed, no pushmatrix, no translate, scale etc. What is the fastest way possible to convert the following code into a 100% opengl es 2.0 compatible way - just the todo part?

 

I dont think its a good way to do for every character two matrix operations (scale and translate) and one operation to reset the matrix before the drawing. Is there a way to improve that - can these be moved to the shader somehow ?
 

	
	private void drawText(String text, float x, float y, float scale, HorizontalAlignment halign, VerticalAlignment valign) {
		// Enable alpha blending
		GL11.glEnable(GL11.GL_BLEND);

		// Enable vertex buffer - will also enabled client state for texture and vertex array
		fontVBO.enable();

		// Set white color
		GL11.glColor4f(1f, 1f, 1f, 1f);

		// Calculate text sizes in world coordinates
		float textSizeX = getTextWidth(text, scale);
		float textSizeY = getTextHeight(text, scale);

		// Calculate starting text x and y offset in world coordinates
		float sxoffset = -textSizeX * 0.5f;
		float syoffset = 0f;
		if (HorizontalAlignment.Left.equals(halign)) {
			sxoffset += textSizeX * 0.5f;
		} else if (HorizontalAlignment.Right.equals(halign)) {
			sxoffset -= textSizeX * 0.5f;
		}
		if (VerticalAlignment.Bottom.equals(valign)) {
			syoffset = textSizeY * 0.5f;
		} else if (VerticalAlignment.Top.equals(valign)) {
			syoffset = -textSizeY * 0.5f;
		}

		// Enable bitmap font texture
		fontTex.enable(0);
		
		// Enable sdf shader when enabled
		if (sdfEnabled) {
			sdfShader.enable();
			sdfShader.setUniform1i(sdfShaderTex0Location, 0);
		}
		
		// TODO: Rendering the characters - each char is moved and scaled in immediate mode which does not work with opengl es 2.0!!!
		float xoffset = sxoffset;
		float yoffset = syoffset;
		for (int i = 0; i < text.length(); i++) {
			BitmapFontChar fontChar = bitmapFonts.get(text.codePointAt(i));
			GL11.glPushMatrix();
			GL11.glTranslatef(x + xoffset + fontChar.getAdvance() * scale * 0.5f, y + yoffset, 0f);
			GL11.glScalef(scale, scale, 1f);
			GL11.glDrawArrays(GL11.GL_QUADS, fontChar.getVboOffset(), 4);
			GL11.glPopMatrix();
			xoffset += fontChar.getAdvance() * scale;
		}
		
		// Disable sdf shader when enabled
		if (sdfEnabled) {
			sdfShader.disable();
		}

		// Disable bitmap font texture
		fontTex.disable(0);

		/*
		GL11.glPolygonMode( GL11.GL_FRONT, GL11.GL_LINE );
		xoffset = sxoffset;
		yoffset = syoffset;
		for (int i = 0; i < text.length(); i++) {
			BitmapFontChar fontChar = bitmapFonts.get(text.codePointAt(i));
			GL11.glPushMatrix();
			GL11.glTranslatef(x + xoffset + fontChar.getAdvance() * 0.5f, y + yoffset, 0f);
			GL11.glDrawArrays(GL11.GL_QUADS, fontChar.getVboOffset(), 4);
			GL11.glPopMatrix();
			xoffset += fontChar.getAdvance();
			//yoffset -= 0.01f;
		}
		GL11.glPolygonMode( GL11.GL_FRONT, GL11.GL_FILL );
		*/

		// Disable vertex buffer - will also disable client state for texture and vertex array
		fontVBO.disable();

		// Disable alpha blending
		GL11.glDisable(GL11.GL_BLEND);
	}
Edited by Finalspace

Share this post


Link to post
Share on other sites
Advertisement

Create the matrix with some other matrix library, that is opengl compatible.

 

Then add something like this to your shader:

 

  gl_Position = u_matrix * a_position;

 

Then you should be able to set your matrix with setUniform and everything should work as before.

Share this post


Link to post
Share on other sites

I have already done this, but is this really the fastest way to do this?

				// Render chars
				float xoffset = sxoffset;
				float yoffset = syoffset;
				for (int i = 0; i < text.length(); i++) {
					TextureFontChar tfc = texFont.getChar(text.codePointAt(i));
					if (tfc == null) {
						// Char is not found, use first one which should the space character
						tfc = texFont.getChar(0);
					}
					currentMatrix.set(orthoMatrix);
					currentMatrix.translate(x + xoffset + tfc.getAdvance() * 0.5f * scale, y + yoffset, 0f);
					currentMatrix.scale(scale, scale, 1f);
					renderer.setTransform(currentMatrix);
					renderer.drawVertexArray(ElementType.Quad, tfc.getVboOffset(), 4);
					xoffset += tfc.getAdvance() * 2f * scale;
				}

Edited by Finalspace

Share this post


Link to post
Share on other sites
Can't you just set up your quads first and then call just one DrawArrays for the whole screen full of text?
You can make it that whenever you call your text drawing code, it does NOT draw it but builds up the quad array. The text can then be all drawn with one call before you swap buffers, or whenever you like of course.

Share this post


Link to post
Share on other sites

Ah, sorry, I thought you meant "least change" with fastest.

 

If you are not animating the individual characters every frame, it would be faster to generate the vertexes into a vertex-array, and then re-use that until the text has to be changed.

Edited by Olof Hedman

Share this post


Link to post
Share on other sites

Ah, sorry, I thought you meant "least change" with fastest.

 

If you are not animating the individual characters every frame, it would be faster to generate the vertexes into a vertex-array, and then re-use that until the text has to be changed.

 

This may work to modify the vertex buffer and fill it with all the letter quads - should be faster than using 2 matrix operations per letter. Why i havent thought about that.... thanks for that hint! The only thing which sucks - filling the vertex buffer with java is a pain in the pass :-(

 

This is so .... inconvenient (This is done once to create the letters from the bitmap font in the vertex buffer initialy):

// Creating a vertex buffer for all letters/quads
fontVBO = renderer.createVertexBuffer(false, vertexCount, VertexBufferFormat.TEX2_VERTEX4_PAD2);

// Creating a damn byte buffer which is required for the fill vertex buffer method
ByteBuffer vertBuffer = ByteBuffer.allocateDirect(VertexBufferFormat.TEX2_VERTEX4_PAD2.getStride() * vertexCount).order(ByteOrder.nativeOrder());
		
// We want to fill floats into the byte buffer - so we need to convert it back to a float buffer -.-
FloatBuffer fontVertices = vertBuffer.asFloatBuffer();

// Put stuff in it
...
fontVertices.put(new float[] { u, v, x, y, z, w, 0f, 0f });
...

// Finally flip the buffer to write the bytes left to the final byte buffer
// This will also reset the postition to zero
fontVertices.flip();

// And lastly fill the vertex buffer with that byte buffer content
fontVBO.fill(vertBuffer);

Share this post


Link to post
Share on other sites
Sign in to follow this  

  • Advertisement
  • Advertisement
  • Popular Tags

  • Advertisement
  • Popular Now

  • Similar Content

    • By QQemka
      Hello. I am coding a small thingy in my spare time. All i want to achieve is to load a heightmap (as the lowest possible walking terrain), some static meshes (elements of the environment) and a dynamic character (meaning i can move, collide with heightmap/static meshes and hold a varying item in a hand ). Got a bunch of questions, or rather problems i can't find solution to myself. Nearly all are deal with graphics/gpu, not the coding part. My c++ is on high enough level.
      Let's go:
      Heightmap - i obviously want it to be textured, size is hardcoded to 256x256 squares. I can't have one huge texture stretched over entire terrain cause every pixel would be enormous. Thats why i decided to use 2 specified textures. First will be a tileset consisting of 16 square tiles (u v range from 0 to 0.25 for first tile and so on) and second a 256x256 buffer with 0-15 value representing index of the tile from tileset for every heigtmap square. Problem is, how do i blend the edges nicely and make some computationally cheap changes so its not obvious there are only 16 tiles? Is it possible to generate such terrain with some existing program?
      Collisions - i want to use bounding sphere and aabb. But should i store them for a model or entity instance? Meaning i have 20 same trees spawned using the same tree model, but every entity got its own transformation (position, scale etc). Storing collision component per instance grats faster access + is precalculated and transformed (takes additional memory, but who cares?), so i stick with this, right? What should i do if object is dynamically rotated? The aabb is no longer aligned and calculating per vertex min/max everytime object rotates/scales is pretty expensive, right?
      Drawing aabb - problem similar to above (storing aabb data per instance or model). This time in my opinion per model is enough since every instance also does not have own vertex buffer but uses the shared one (so 20 trees share reference to one tree model). So rendering aabb is about taking the model's aabb, transforming with instance matrix and voila. What about aabb vertex buffer (this is more of a cosmetic question, just curious, bumped onto it in time of writing this). Is it better to make it as 8 points and index buffer (12 lines), or only 2 vertices with min/max x/y/z and having the shaders dynamically generate 6 other vertices and draw the box? Or maybe there should be just ONE 1x1x1 cube box template moved/scaled per entity?
      What if one model got a diffuse texture and a normal map, and other has only diffuse? Should i pass some bool flag to shader with that info, or just assume that my game supports only diffuse maps without fancy stuff?
      There were several more but i forgot/solved them at time of writing
      Thanks in advance
    • By RenanRR
      Hi All,
      I'm reading the tutorials from learnOpengl site (nice site) and I'm having a question on the camera (https://learnopengl.com/Getting-started/Camera).
      I always saw the camera being manipulated with the lookat, but in tutorial I saw the camera being changed through the MVP arrays, which do not seem to be camera, but rather the scene that changes:
      Vertex Shader:
      #version 330 core layout (location = 0) in vec3 aPos; layout (location = 1) in vec2 aTexCoord; out vec2 TexCoord; uniform mat4 model; uniform mat4 view; uniform mat4 projection; void main() { gl_Position = projection * view * model * vec4(aPos, 1.0f); TexCoord = vec2(aTexCoord.x, aTexCoord.y); } then, the matrix manipulated:
      ..... glm::mat4 projection = glm::perspective(glm::radians(fov), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f); ourShader.setMat4("projection", projection); .... glm::mat4 view = glm::lookAt(cameraPos, cameraPos + cameraFront, cameraUp); ourShader.setMat4("view", view); .... model = glm::rotate(model, glm::radians(angle), glm::vec3(1.0f, 0.3f, 0.5f)); ourShader.setMat4("model", model);  
      So, some doubts:
      - Why use it like that?
      - Is it okay to manipulate the camera that way?
      -in this way, are not the vertex's positions that changes instead of the camera?
      - I need to pass MVP to all shaders of object in my scenes ?
       
      What it seems, is that the camera stands still and the scenery that changes...
      it's right?
       
       
      Thank you
       
    • By dpadam450
      Sampling a floating point texture where the alpha channel holds 4-bytes of packed data into the float. I don't know how to cast the raw memory to treat it as an integer so I can perform bit-shifting operations.

      int rgbValue = int(textureSample.w);//4 bytes of data packed as color
      // algorithm might not be correct and endianness might need switching.
      vec3 extractedData = vec3(  rgbValue & 0xFF000000,  (rgbValue << 8) & 0xFF000000, (rgbValue << 16) & 0xFF000000);
      extractedData /= 255.0f;
    • By Devashish Khandelwal
      While writing a simple renderer using OpenGL, I faced an issue with the glGetUniformLocation function. For some reason, the location is coming to be -1.
      Anyone has any idea .. what should I do?
    • By Andrey OGL_D3D
      Hi all!
      I try to use the Sun shafts effects via post process in my 3DEngine, but i have some artefacts on final image(Please see attached images).
      The effect contains the following passes:
      1) Depth scene pass;
      2) "Shafts pass" Using DepthPass Texture + RGBA BackBuffer texture.
      3) Shafts pass texture +  RGBA BackBuffer texture.
      Shafts shader for 2 pass:
      // uniform sampler2D FullSampler; // RGBA Back Buffer uniform sampler2D DepthSampler; varying vec2 tex; #ifndef saturate float saturate(float val) {     return clamp(val, 0.0, 1.0); } #endif void main(void) {     vec2 uv = tex;     float sceneDepth = texture2D(DepthSampler, uv.xy).r;     vec4  scene        = texture2D(FullSampler, tex);     float fShaftsMask     = (1.0 - sceneDepth);     gl_FragColor = vec4( scene.xyz * saturate(sceneDepth), fShaftsMask ); } final shader:
      // uniform sampler2D FullSampler; // RGBA Back Buffer uniform sampler2D BlurSampler; // shafts sampler varying vec4 Sun_pos; const vec4    ShaftParams = vec4(0.1,2.0,0.1,2.0); varying vec2 Tex_UV; #ifndef saturate  float saturate(float val) {     return clamp(val, 0.0, 1.0); } #endif vec4 blendSoftLight(vec4 a, vec4 b) {   vec4 c = 2.0 * a * b + a * a * (1.0 - 2.0 * b);   vec4 d = sqrt(a) * (2.0 * b - 1.0) + 2.0 * a * (1.0 - b);       // TODO: To look in Crysis what it the shit???   //return ( b < 0.5 )? c : d;   return any(lessThan(b, vec4(0.5,0.5,0.5,0.5)))? c : d; } void main(void) {     vec4 sun_pos = Sun_pos;     vec2    sunPosProj = sun_pos.xy;     //float    sign = sun_pos.w;     float    sign = 1.0;     vec2    sunVec = sunPosProj.xy - (Tex_UV.xy - vec2(0.5, 0.5));     float    sunDist = saturate(sign) * saturate( 1.0 - saturate(length(sunVec) * ShaftParams.y ));     sunVec *= ShaftParams.x * sign;     vec4 accum;     vec2 tc = Tex_UV.xy;     tc += sunVec;     accum = texture2D(BlurSampler, tc);     tc += sunVec;     accum += texture2D(BlurSampler, tc) * 0.875;     tc += sunVec;     accum += texture2D(BlurSampler, tc) * 0.75;     tc += sunVec;     accum += texture2D(BlurSampler, tc) * 0.625;     tc += sunVec;     accum += texture2D(BlurSampler, tc) * 0.5;     tc += sunVec;     accum += texture2D(BlurSampler, tc) * 0.375;     tc += sunVec;     accum += texture2D(BlurSampler, tc) * 0.25;     tc += sunVec;     accum += texture2D(BlurSampler, tc) * 0.125;     accum  *= 0.25 * vec4(sunDist, sunDist, sunDist, 1.0);           accum.w += 1.0 - saturate(saturate(sign * 0.1 + 0.9));     vec4    cScreen = texture2D(FullSampler, Tex_UV.xy);           vec4    cSunShafts = accum;     float fShaftsMask = saturate(1.00001 - cSunShafts.w) * ShaftParams.z * 2.0;              float fBlend = cSunShafts.w;     vec4 sunColor = vec4(0.9, 0.8, 0.6, 1.0);     accum =  cScreen + cSunShafts.xyzz * ShaftParams.w * sunColor * (1.0 - cScreen);     accum = blendSoftLight(accum, sunColor * fShaftsMask * 0.5 + 0.5);     gl_FragColor = accum; } Demo project:
      Demo Project
      Shaders for postprocess Shaders/SunShaft/
      What i do wrong ?
      Thanks!
       


  • Advertisement