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function BlurredMipmapDemo(deviceIndexOrMoviename, gazeRadius, customMipmap)
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% BlurredMipmapDemo - Show blurring of live video or movies via adaptive mipmapping.
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% This demo shows how to selectively blur regions of a live video stream
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% captured from an attached camera, or a live playing movie. The method
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% employed here uses a GLSL shader to select an individual blur level for
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% each output pixel. Pixels close to the mouse cursor (which simulates gaze
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% position, e.g., as aquired by an eyetracker) will be drawn sharp, whereas
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% pixels at larger radial distance will be drawn increasingly unsharp by
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% low-pass filtering them.
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% The method of blurring here is computationally efficient and fast,
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% because it generates and uses a image resolution pyramid to precompute
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% different versions of the video image at different resolutions. Then the
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% shader just looks up color information for each individual output pixel
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% from the proper "level of detail" in the pyramid of low pass filtered
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% images. The resolution pyramid is auto-generated in a fast, GPU
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% accelerated way for each image by use of OpenGL "mip-mapping". This
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% method uses a fixed low-pass filter for downsampling, usually a box
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% filter, but the exact type of filter used is system dependent and can
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% vary across different graphics cards, graphics driver versions or
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% The demo requires recent graphics hardware and won't work on old graphics
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% BlurredMipmapDemo([deviceIndexOrMoviename=0][, gazeRadius=25][, customMipmap=0])
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% 'gazeRadius' Some falloff radius in pixels. Controls how quickly the
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% resolution degrades with increasing distance from the cursorposition.
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% Smaller values give a smaller simulated "foveal area".
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% 'deviceIndexOrMoviename' = Optional: Either the index of the video
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% capture device, or the full path to a movie file. Defaults to
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% auto-selected default video source.
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% 'customMipmap' Optional: If non-zero, use a custom shader for
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% downsampling during mipmap building, instead of the relatively simple
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% builtin filter of the GPU.
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% Press any key to finish the demo.
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% 28.08.2012 mk Written.
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% Select maximum display id for output:
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screenId = max(Screen('Screens'));
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if nargin < 1 || isempty(deviceIndexOrMoviename)
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deviceIndexOrMoviename = [];
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if nargin < 2 || isempty(gazeRadius)
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if nargin < 3 || isempty(customMipmap)
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% Is it a movie file name?
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if ischar(deviceIndexOrMoviename)
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% Yes: Playback the movie.
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moviename = deviceIndexOrMoviename;
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% No: Nothing or a numeric video capture deviceindex. Do videocapture.
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% Use automatic mipmap generation by GPU driver builtin method:
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% Don't generate mipmaps automatically, roll our own downsampling:
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% This is the correct flag for 'GetMovieImage':
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% This is the correct flag for 'GetCapturedImage':
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% Open onscreen window with black background color:
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win = Screen('OpenWindow', screenId, 0);
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[w, h] = Screen('WindowSize', win); %#ok<*ASGLU>
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% Load & Create a GLSL shader for adaptive mipmap lookup:
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shaderpath = fileparts(mfilename('fullpath'));
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shader = LoadGLSLProgramFromFiles([shaderpath filesep 'BlurredMipmapDemoShader'], 1);
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% Bind texture unit 0 to shader as input source for the mip-mapped video image:
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glUseProgram(shader);
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glUniform1i(glGetUniformLocation(shader, 'Image'), 0);
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% Load & Create a GLSL shader for downsampling during MipMap pyramid
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% creation. This specific example shader uses a 3-by-3 gaussian filter
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% kernel with a standard deviation of 1.0:
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mipmapshader = LoadGLSLProgramFromFiles([shaderpath filesep 'MipMapDownsamplingShader.frag.txt'], 1);
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% Open movie and start its playback:
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movie = Screen('OpenMovie', win, moviename);
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Screen('PlayMovie', movie, 1, 1, 1);
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% Open video capture device 'deviceIndex':
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grabber = Screen('OpenVideoCapture', win, deviceIndexOrMoviename);
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% Start video capture:
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Screen('StartVideoCapture', grabber, realmax, 1);
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% Change cursor to a cross-hair:
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ShowCursor('CrossHair');
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% Repeat until keypress or timeout of 10 minutes:
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while ((GetSecs - t) < 600) && ~KbCheck
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% Wait for next video image or movie frame. The first '1' asks to
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% wait blocking for the next image, instead of polling. 'tex' is
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% returned for recycling to increase efficiency. The specialMode
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% flag '1' asks Screen() to return the texture as a GL_TEXTURE_2D
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% texture. This is needed for the automatic mip-mapping for
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% low-pass filtering to work:
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% Get next movie frame:
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tex = Screen('GetMovieImage', win, movie, 1, [], 1 + dontautomip);
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% Get next video frame:
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tex = Screen('GetCapturedImage', win, grabber, 1, tex, 1 + dontautomip);
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% Valid 'tex'ture with new videoframe returned?
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% Yes. Get current "center of gaze" as simulated by the current
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% mouse cursor position:
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[gazeX, gazeY] = GetMouse(win);
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% Flip y-axis direction -- Shader has origin bottom-left, not
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% top-left as GetMouse():
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% Need to create mipmaps ourselves?
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% Yes: Use PTB's utility function for shader-based mipmap
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% generation with more control, but less performance. We
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% use 'mipmapshader' as downsampling shader, and '1' enable
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% bilinear filtering for the shader:
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CreateResolutionPyramid(tex, mipmapshader, 1);
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% Draw new video texture from framegrabber. Apply GLSL 'shader'
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% during drawing. Use filterMode 3: This will automatically
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% generate the mipmap image resolution pyramid, then use the
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% 'shader' to adaptively lookup lowpass filtered pixels from
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% the different blur-levels of the image pyramid to simulate
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% typical foveation effect of decreasing resolution with
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% increasing distance to center of fixation. We pass gaze
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% center (gazeX, gazeY) and radius of foveation 'gazeRadius' as
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% auxParameters. auxParameters must always have a multiple of 4
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% components, so we add a zero value for padding to length 4:
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Screen('DrawTexture', win, tex, [], [], [], 3, [], [], shader, [], [gazeX, gazeY, gazeRadius, 0]);
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% Need to close texture if movie is played back:
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Screen('Close', tex);
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% Show it at next video refresh:
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% Increase frame counter:
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% Display some timing stats:
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telapsed = GetSecs - t;
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avgfps = count / telapsed;
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fprintf('Average frames per second: %f.\n', avgfps);
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% Stop and close movie:
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Screen('PlayMovie', movie, 0);
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Screen('CloseMovie', movie);
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% Stop and close video source:
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Screen('StopVideoCapture', grabber);
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Screen('CloseVideoCapture', grabber);
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% Close down everything else:
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% Error handling, emergency shutdown:
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psychrethrow(psychlasterror);
added
removed
Psychtoolbox/PsychDemos/BlurredMipmapDemo.m
