I would like to draw lines with a glow around them as in the following image:
What is the way to do it with OpenGL ES 2.0?
There are a number of ways to do this. One popular method is to draw the lines you want to have a glow around them into a texture-backed frame buffer. Then post-process the texture by blurring it and adding the blurred copy to the original copy.
Related
I have two simple translucent circle sprites that I'm using as fake shadows (shown below) under some characters (not shown below). When the characters get close enough, sometimes their shadow circles can overlap - which is fine - but thanks to the default blending it doesn't look right. I want the shadow circles that do overlap to be visually merged/mixed so they maintain the same opacity, but instead they add together where they overlap like this: I have to imagine there's some way to make this work with a shader, but I'm so bad at shaders that I can't seem to figure it out. Does anyone know how to solve this?
In a webpage created with node/webpack, vega-lite, and vegaEmbed, I have a layer with rect marks with short annotations inside them using text marks. I'd like to clip the text to its surrounding rect but haven't figured out a way to do this and hope someone can point me in the right direction.
I realize text has a limit property in pixel units. If I could determine the pixel units of my rect marks (I don't know how to do this), using limit seems like a reasonable approach.
Also, if I knew the pixel extents of my rectangle, I can then write code to align the text within the rect which would be desirable. Currently I just use the same x as the rect, with a dx offset.
I've read about background for text which is a similar problem, but not the same.
I am developing a game using Phaser where a user is rendered a triangular canvas. User can crop this canvas to any possible shape by drawing any crop pattern on the canvas. Besides this, i need to get this cropped canvas in suitable data format to be used as an image to render and also trace changes made on this canvas for undoing puspose.
Any help to get this through will be appreciated.
Thanks in advance.
Initial canvas
Canvas after crop
Cropped canvas used to create new canvas
So it's like folding a piece of paper and then cutting it so it looks like a snowflake? Interesting idea.
I think you could either use BitmapData to draw the initial cut out, then copy that bitmap 6 (or 12?) times and rotate and flip x-axis to construct the rest. Though maybe there will be seems, so like small lines, between the parts idk.
Another appproach would be to keep track of the initial cutlines like vectors. Then use math/trigonometry to calculate the result. No idea how to do this though, sorry.
I have a multiviewport OpenGL modeler application. It has three different viewports : perspective, front and top. Now I want to paint a label for each viewport and not succeeding in doing it.
What is the best way to print a label for each different perspective?
EDITED : The result
Here is the result of my attempt:
I don't understand why the perspective viewport label got scrambled like that. And, Actually I want to draw it in the upper left corner. How do I accomplished this, because I think it want 3D coordinate... is that right? Here is my code of drawing the label
glColor3f(1,0,0);
glDisable(GL_DEPTH_TEST);
glDepthMask(GL_FALSE);
glRasterPos2f(0,0);
glPushAttrib(GL_LIST_BIT); // Pushes The Display List Bits
glListBase(base - 32); // Sets The Base Character to 32
glCallLists(strlen("Perspective"), GL_UNSIGNED_BYTE, "Perspective"); // Draws The Display List Textstrlen(label)
glPopAttrib();
I use the code from here http://nehe.gamedev.net/data/lessons/lesson.asp?lesson=13
thanks
For each viewport switch into a projection that allows you to supply "viewport space" coordinates, disable depth testing (glDisable(GL_DEPTH_TEST)) and depth writes (glDepthMask(GL_FALSE)) and draw the text using one of the methods used to draw text in OpenGL (texture mapped fonts, rendering the full text into a texture drawing that one, draw glyphs as actual geometry).
Along with #datenwolf's excellent answer, I'd add just one bit of advice: rather than drawing the label in the viewport, it's usually easier (and often looks better) to draw the label just outside the viewport. This avoids the label covering anything in the viewport, and makes it easy to get nice, cleanly anti-aliased text (which you can normally do in OpenGL as well, but it's more difficult).
If you decide you need to draw the text inside the viewport anyway, I'll add just one minor detail to what #datenwolf said: since you generally do want your text anti-aliased (even if the rest of the picture isn't) you generally want to draw the label after all the other geometry of the picture itself. If you haven't turned on anti-aliasing otherwise, you generally will want to turn it on for drawing the text.
I've been stumbling over this for a while and was wondering if anyone has run into this problem before.
The application I'm working on is divided into multiple data plots and a single timeline at the bottom of the screen. Each plot (which is actually multiple textures layered on top of each other) as well as the timeline is rendered to a separate texture. The timeline texture is rendered first, followed by each of the plot textures from the top of the screen to the bottom. I am using DXUT and DirectX9 (March 2009).
After adding time text to the timeline texture, I noticed that the text was repeated in the title bar of every data plot. Here's a screencap of a portion of the display, it shows just a single plot, but the text repeats on every plot opened:
It seems like it is tied directly to the DrawText being called in the timeline's render function. I do use relative coordinates as the rect being passed to DrawText, but since I've already set the render target to the desired texture it should only affect the current texture. Not every texture rendered afterward.
Has anyone ever run into any problems similar to this using D3DXFont?
EDIT: After some more experimentation, it looks like it has something to do with the Z buffer. By adding D3DCLEAR_ZBUFFER to the clear on each texture surface, the duplicate text is gone. While the problem seems bypassed for now, I'm still curious as to why the Z buffer for a completely separate texture was being written during my DrawText call.
The Z Buffer state is persistent.
For example,
SetDepthStencilSurface(X)
SetRenderTarget(A)
Draw()
SetRenderTarget(B)
Draw()
Both Draw calls will use the same depth buffer.
The DrawText is not changing the depth buffer that you have set. It assumes you meant to do what you did.