I have four 1920 x 1080 PImage instances with alpha channel that I have to "blend" together at runtime on every frame.

You may be tempted to ask why - and I may be able to answer it but it could be a long explanation.

I thought about having a PImage and just "copy" the others into it on every frame.  In Flash you can copy pixels from an image extremely fast.  But it looks like copy() ignores the alpha channel.  I have tried blend() and it is very slow.

Could a custom shader do this very fast??

Best,

Sammi

I think I am misunderstanding how fragment shaders work.  I thought that this shader would not do anything.  Simply set the color of each pixel to whatever it was before:

2. #define PROCESSING_TEXTURE_SHADER
3. 
   
4. uniform sampler2D texture;
5. varying vec4 vertColor;
6. varying vec4 vertTexCoord;
7. 
   
8. void main() 
9. {
10. vec4 rgba = texture2D(texture, vertTexCoord.st).rgba;
11. gl_FragColor = rgba;
13. }
14. 
    

But it seems to do something more than that.  As I apply this filter to my red PGraphics instance it becomes gray over time.  

Why is that?

Best,

Sammi

Best,

Sammi

Although I have experimented with Processing in the past I am only a beginner.  I have been a Flash developer for many many years and I guess I am a bit spoiled because layer composition is so easy there.

I have browsed the internet for a solution to my problem but haven't found a good answer.  I guess I am looking for the wrong things so I was hoping someone could help me. So here goes:

In Processing a common way to create a fade/trail is to draw a semitransparent rectangle over the sketch in every run.  This is fine if you want everything to fade.  I don't want that.  I have a map in the background (full screen) and on top of that I am trying to draw graphics (full screen) that fades out over time, leaving a trail.  I think I am supposed to use createGraphics() and create an off screen buffer for the graphic that I want to fade over time, and use the semitransparent trick on that graphic.  Then I would use image() in the main draw loop to add the graphic on top of the map.

This works, but of course not quite.  The semitransparent rectangle is exactly that - semi transparent - and therefor visible over the map.

Is there a simple and fast trick that I am missing when it comes to layering like this?  I am sure it is not very effective to manipulate all the 1920x1080 pixels in the top layer and reducing the alpha over time.

Best,

Sammi

    

I am working on a project that requires a variable speed in video playback.  This can be achieved with Movie.speed().  I have two questions regarding it that I was hoping someone would shed a light on:

- What limits the maximum speed?  For my HD video I see no speed difference once I go over speed(2).  I can go from -2 up to 2 but anything outside that range does not do anything.  Is this a CPU thing so smaller videos could go faster?

- What codec is best for a video that should play backwards and forwards at speeds up to maybe 10x.  ( Matroska x264? )

Best,

Sammi

I am wondering how you manage multiple versions of Processing on your computers?  I have been doing some work in 1.5.1 but now, obviously, I want to start with 2.0b1.  I have both versions in my C:Program FilesProcessing folder:

- processing-1.5.1

- processing-2.0b1

This works fine ofcourse.The problem is that the sketchbook location, as well as many preferences is stored in 

C:USammiAppDataRoamingProcessingpreferences.txt and hence common for all versions of Processing.

Is there a way around this?  Or should I not bother?

Best

I am new to processing and thinking if it is wise to jump straight to the alphas.

Best