Mask does not appear in syphon feed.

[Tenkir]

I have an alpha mask that I'm using on the canvas. It works fine in the processing image, but when viewing the syphon feed, I only see the base layer. The mask and anything after are not rendered.

import processing.video.*;
import codeanticode.syphon.*;

PGraphics canvas;
SyphonServer server;
PImage mask;
PImage lines;
PImage backdrop;
Movie background;

void setup() {
  size(1920,1080, P3D);
  canvas = createGraphics(1920, 1080, P3D);
  mask = loadImage("alpha_mask.png");
  backdrop = loadImage("white_backdrop.png");
  background = new Movie(this, "finalimage_1.mov");
  background.loop();
  
  // Create syhpon server to send frames out.
  server = new SyphonServer(this, "Processing Syphon");
}

void draw() {
  canvas.beginDraw();
  canvas.background(100);
  canvas.image(background, 420, 0);
  canvas.mask(mask);
  canvas.image(backdrop, 0, 0);
  canvas.endDraw();
  image(canvas, 0, 0);
  server.sendImage(canvas);
}

void movieEvent(Movie m) {
  m.read();
}

Processing Window:

MadMapper:

[vade]

Ensure both apps agree on premultiplied vs unpremultiplied alpha. No idea what Processing's mask option does but my guess is your alpha is not premultiplied in Processing.

[vade]

Ensure your target app and destination app both use premultiplied or unpremulitplied alpha. Syphon doesn't care what you use but you do have to agree.

…

Sent from my iPhone

On Sep 22, 2017, at 6:07 AM, Jonathan Blair ***@***.***> wrote: I have an alpha mask that I'm using on the canvas. It works fine in the processing image, but when viewing the syphon feed, I only see the base layer. The mask and anything after are not rendered. import processing.video.*; import codeanticode.syphon.*; PGraphics canvas; SyphonServer server; PImage mask; PImage lines; PImage backdrop; Movie background; void setup() { size(1920,1080, P3D); canvas = createGraphics(1920, 1080, P3D); mask = loadImage("alpha_mask.png"); backdrop = loadImage("white_backdrop.png"); background = new Movie(this, "finalimage_1.mov"); background.loop(); // Create syhpon server to send frames out. server = new SyphonServer(this, "Processing Syphon"); } void draw() { canvas.beginDraw(); canvas.background(100); //canvas.image(background, 420, 0); //canvas.mask(mask); canvas.image(backdrop, 0, 0); canvas.endDraw(); image(canvas, 0, 0); server.sendImage(canvas); } void movieEvent(Movie m) { m.read(); } — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub, or mute the thread.

[bangnoise]

I thought this sounded like it might be a real issue, but I can't get canvas.mask() to have any effect within Processing. If you can attach a minimal sketch folder with images to demonstrate the problem, I'll take a look.

[codeanticode]

Revising very old issues, just for fun :-)

In this case, what's happening is that the texture that's backing the rendering surface (either onscreen or offscreen) is not updated with the output from the filter (mask() in P2D/P3D internally calls filter()), for some reason (it should, so opened a bug about this in the main processing4 repo: benfry/processing4#449).

But, it gets full updated in the next frame, so one temporary workaround is to move the server.sendImage(canvas) call to the top of the draw() function.

A shorter example demonstrating the workaround. Original code (filter output does not show up in the receiveFrames sketch)

import codeanticode.syphon.*;

PGraphics canvas;
SyphonServer server;

PShader edges;

void setup() { 
  size(400,400, P3D);
  canvas = createGraphics(400, 400, P3D);
  edges = loadShader("edges.glsl");
  
  // Create syhpon server to send frames out.
  server = new SyphonServer(this, "Processing Syphon");
}

void draw() {  
  canvas.beginDraw();
  canvas.background(127);
  canvas.lights();
  canvas.translate(width/2, height/2);
  canvas.rotateX(frameCount * 0.01);
  canvas.rotateY(frameCount * 0.01);  
  canvas.box(150);
  canvas.filter(THRESHOLD);
  canvas.endDraw();
  image(canvas, 0, 0);
 server.sendImage(canvas);
}

Modified code (it works as expected):

void draw() {
  server.sendImage(canvas);
  canvas.beginDraw();
  canvas.background(127);
  ...

Also worth noting that the issue affects both the filter() function that takes only predetermined filters and the one with the PShader argument.