Android: How to get round stroke corners in canvas

When you draw a path with a bigger line stroke width, you might notice uggly edges.

android canvas no round stroke corners no round stroke corners

In order to get them round you simply need to change the stroke join to round. Here are some default settings I’m using in my Doodle Drawer app.

At the end it should look like this:

round cornersround stroke corners

Doodle Drawer

Inspired by Harmony from Mr. Doob (Ricardo Cabello) I made a little app called ‘Doodle Drawer’. The basic idea  for some brushes is that it connects lines that has been drawn already and in case they’re close enough.

doodle drawersilly doodle

Shader to software skinning method conversation

An almost monolog on stackoverflow helped me to get skeleton animations at least usably working in render demo that I’ve put up in android market. By the way on how the shader computes mat4 * vec4 can be found in the opengles shading language specification.

All right I’ve got a mesh with around 8000+ vertices, it’s sekelon with up to 128 bones and all it’s bone keyframe transformations up to 400 each animation.

Ahri SkeletonAhri Skeleton

Ahri MeshAhri Mesh

On desktop I could use this in vertex shader in order to compute the skinning:

As you can see there are a lot of bones. On android I don’t have the luxury of wasting variables to make simple lookups. I’d need 128 mat4  * 4 vec4 = 512 shader uniform vector variables and my samsung galaxy s2 only supports 304. Anyway I can think of 2 solutions:

  1. divide the mesh into an ‘ok’ amount of bones and render the mesh with less bone matrices
  2. do the skinning in software and update the vertex/normal buffers

I’d prefer the first solution, because I’d have to update merely the bone matrices uniform each frame instead of the entire vertex buffer. At this point however I have no idea how to divide the mesh because each vertex can have up to 4 bone influences and so I implemented the 2nd choice for now. Work in progress…

Here is the equivalent java code:

libgdx and BufferUtils.copy()

While trying to increase the speed of skeleton animations in my android opengl render engine I’ve stumbled uppon some issues with android < v3.0 FloatBuffer.put(). It states the following methods to update the buffers and it speeds:

The same benchmark produced the following timings on a Nexus One with Android 2.2:

  • FloatBuffer.put( float value ): 6.876 secs
  • FloatBuffer.put(int index, float value): 7.006 secs
  • FloatBuffer.put( float[] values ): 6.800 sec
  • IntBuffer.put( int[] values): 1.479 secs
  • BufferUtils.copy(): 0.067 secs

In order to use the BufferUtils.copy() methode provided in libgdx library you need the gdx.jar, gdx-backend-android.jar, which you should add as library to your android project, and the compiled libs in the right place.

Also call


actually before you do anything with libgdx classes, since they are using pre-compiled code.