Writing to video files

Prerequisites

Add the openrndr-ffmpeg library to your project. Make sure ffmpeg is installed on your system.

Writing to video using render targets

fun main() = application {
    program {
        val videoWriter = VideoWriter.create().size(width, height).output("output.mp4").start()
        
        val videoTarget = renderTarget(width, height) {
            colorBuffer()
            depthBuffer()
        }
        

        var frame = 0
        extend {
            drawer.isolatedWithTarget(videoTarget) {
                clear(ColorRGBa.BLACK)
                rectangle(40.0 + frame, 40.0, 100.0, 100.0)
            }
            
            videoWriter.frame(videoTarget.colorBuffer(0))
            drawer.image(videoTarget.colorBuffer(0))
            frame++
            if (frame == 100) {
                videoWriter.stop()
                application.exit()
            }
        }
    }
}

The ScreenRecorder extension

A much simpler way of writing your program’s output to video is offered by the ScreenRecorder extension. The extension creates video files named after your Program class name plus the date. For example: MyProgram-2018-04-11-11.31.03.mp4. The video files are located in the current working directory.

To setup the screen recorder you do the following:

fun main() = application {
    program {
        extend(ScreenRecorder())
        extend {// -- whatever you do here ends up in the video
        }
    }
}