1 / 30

3D Game Programming 2D primitive

3D Game Programming 2D primitive. Ming-Te Chi Department of Computer Science,  National Chengchi University. Outline. Imaging and Raster Primitives( 4rd ch7) Alpha and blending ( 4rd ch6 ) ( 5 th ch3 ). IMAGING AND RASTER PRIMITIVES. Electromagnetic spectrum. Image from wiki.

cai
Download Presentation

3D Game Programming 2D primitive

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. 3D Game Programming2D primitive Ming-Te Chi Department of Computer Science,  National Chengchi University

  2. Outline • Imaging and Raster Primitives(4rd ch7) • Alpha and blending (4rd ch6) (5th ch3)

  3. IMAGING AND RASTER PRIMITIVES

  4. Electromagnetic spectrum Image from wiki

  5. Three-Color Theory • Human visual system has two types of sensors • Rods: • monochromatic, night vision • Cones: • Color sensitive • Three types of cone • Only three values • (the tristimulusvalues) are sent to the brain

  6. Additive / Subtractive color Y M C Subtractive Color Printer Additive Color LCD, projector

  7. RGB color space Green Black (0, 0, 0) Red Blue rgb color cube in another view

  8. HSV color space • HSV • hue,  • Saturation,  • Value, HSV UI

  9. Imaging and Raster Primitives • Describe OpenGL’s raster primitives: • bitmaps • image rectangles • Demonstrate how to get OpenGL to read and render pixel rectangles

  10. Pixel-based primitives • Bitmaps • 2D array of bit masks for pixels • update pixel color based on current color • Images • 2D array of pixel color information • complete color information for each pixel • OpenGL does not understand image formats

  11. Per Vertex Poly. Frag FB Raster CPU DL Texture Pixel Pixel Pipeline • Programmable pixel storage and transfer operations glBitmap(), glDrawPixels() Rasterization (including Pixel Zoom) Pixel Storage Modes Pixel-Transfer Operations (and Pixel Map) Per FragmentOperations FrameBuffer CPU glCopyTex*Image(); TextureMemory glReadPixels(), glCopyPixels()

  12. Positioning Image Primitives glRasterPos3f( x, y, z ) • Raster position transformed like geometry • discarded if raster positionis outside of viewport • may need to fine tuneviewport for desiredresults Raster Position

  13. glWindowPos2f(x, y) • Specify the raster position in window coordinates for pixel operations

  14. height yorig width xorig xmove Rendering Bitmaps glBitmap( width, height, xorig, yorig, xmove, ymove, bitmap ) • render bitmap in current colorat • advance raster position by after rendering

  15. Rendering Fonts using Bitmaps • OpenGL uses bitmaps for font rendering • each character is stored in a display list containing a bitmap • window system specific routines to access system fonts • glXUseXFont() • wglUseFontBitmaps()

  16. Rendering Images glDrawPixels( width, height, format, type, pixels ) • render pixels with lower left of image at current raster position • numerous formats and data typesfor specifying storage in memory • best performance by using format and type that matches hardware height width

  17. Reading Pixels glReadPixels( x, y, width, height, format, type, pixels ) • read pixels from specified (x,y) position in framebuffer • pixels automatically converted from framebuffer format into requested format and type • Framebuffer pixel copy glCopyPixels( x, y, width, height, type )

  18. glCopyPixels() glDrawPixels() Frame Buffer Memory glReadpixels()

  19. RasterPosition glPixelZoom(1.0, -1.0); Pixel Zoom glPixelZoom( x, y ) • expand, shrink or reflect pixelsaround current raster position • fractional zoom supported

  20. Storage and Transfer Modes • Storage modes control accessing memory • byte alignment in host memory • extracting a subimage • Transfer modes allow modify pixel values • scale and bias pixel component values • replace colors using pixel maps

  21. Pixel Packing void glPixelstorei(GLenum pname, GLint param); unpack FrameBuffer Memory pack

  22. ALPHA AND BLENDING

  23. Alpha • An alpha channel, representing transparency information on a per-pixel basis. • Alpha =0: full transparent • Alpha =1 :a fully opaque pixel.

  24. Chroma-keying (Primatte)

  25. Writing Model • Use A component of RGBA (or RGBa) color to store opacity • During rendering we can expand our writing model to use RGBA values blend source blending factor destination component source component Color Buffer destination blending factor

  26. Blending • glBlendFunc(Glenum S, Glenum D); • Cf = (Cs*S) + (Cd*D) • glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); Ex: Cs={Rs, Gs, Bs, As}, Cd ={Rd, Gd, Bd, Ad}, Cf = (Cs*As) + (Cd*(1-As))

  27. B F C C Compositing foreground color alpha matte background plate composite F compositing equation =0 B

  28. B F C C Compositing composite F compositing equation =1 B

  29. Order Dependency • Is this image correct? • Probably not • Polygons are renderedin the order they passdown the pipeline • Blending functionsare order dependent

  30. class RGBApixmap RGBApixmap pic; pic.readBMPFile(“stand.bmp”); pic.setChromaKey(232, 248, 248); //draw glPixelZoom(1.0, 1.0); glWindowPos2i(picX, picY); pic.blend(); // alternative draw pic.blendtex(picX, picY, 1.0, 1.0);

More Related