Game Programming 08 OGRE3D Material in Action 2010 년 2 학기 디지털콘텐츠전공

Rendering in Video Games Depth-Buffered Triangle Rasterization –Virtual Scene –Virtual Camera –Various Light Sources –Visual Properties  Solving the Rendering Equation (Shading Equation)

Rendering in OGRE3D Depth-Buffered Triangle Rasterization –Virtual Scene  createScene() –Virtual Camera  createCamera()/ createViewport() –Various Light Sources  createScene() –Visual Properties  material  Solving the Rendering Equation (OGRE3D engine)

Materials in general The Material controls how objects look in the scene –Basic surface properties such as: reflectance, diffuse color, shininess, etc. –How to use textures What images to be used How many and how to blend them –Special effects such as: Environmental mapping Culling mode filtering

Materials in OGRE SceneManager class manages the list of materials available to the scene To ways of loading a material –Creating and tweaking it by a code MaterialManager –Using a script to be loaded at runtime Material Script

OGRE Material Script: –File name: ‘’*.material ’’ –A text file which describe a material –Easy to define a complex material –Reuse easily for different games How to load –OGRE looks for *.material files in all resource locations. –Call ‘load’ method in order to complete the loading process otherwise, the materials are not available.

Material Script: Format // This is a comment material walls/funkywall1 { // first, preferred technique technique { // first pass pass { ambient diffuse // Texture unit 0 texture_unit { texture wibbly.jpg scroll_anim wave_xform scale sine } // Texture unit 1 (this is a multitexture pass) texture_unit { texture wobbly.png rotate_anim 0.25 colour_op add } // This is a comment material walls/funkywall1 { // first, preferred technique technique { // first pass pass { ambient diffuse // Texture unit 0 texture_unit { texture wibbly.jpg scroll_anim wave_xform scale sine } // Texture unit 1 (this is a multitexture pass) texture_unit { texture wobbly.png rotate_anim 0.25 colour_op add }

Material Script: Name Material name –Should be unique –‘/’ is used for grouping conceptually –‘:’ can be used after the name for inherit from other existing material // This is a comment material walls/funkywall1 { …… } // This is a comment material walls/funkywall1 { …… }

Material Script: Technique Technique –Define how the material looks –Can have multiple techniques used as a fallback or in a different LOD level. –Each Technique is made up of multiple passes // This is a comment material walls/funkywall1 { // first, preferred technique technique { ……… } // second, preferred technique technique { ……… } // This is a comment material walls/funkywall1 { // first, preferred technique technique { ……… } // second, preferred technique technique { ……… }

Material Script: Pass Single Pass –One single rendering with a given setup –A pass has global attributes such as ambient, diffuse, etc. –A pass can have a texture unit or multiple texture units Multiple Passes (1~16 passes) –Rendering can be done multiple times with different setup –The final rendering result will be obtained by compositing every results from the passes. material walls/funkywall1 { technique { // first pass pass { …… } material walls/funkywall1 { technique { // first pass pass { …… }

Material Script: Pass Global attributes –Ambient color Format: ambient ( [ ]| vertexcolour) Example: ambient Default: ambient –Diffuse color Format: diffuse ( [ ]| vertexcolour) Example: diffuse Default: diffuse –Specular color Format: specular ( [ ]| vertexcolour) Example: specular Shininess: any value between 0~128 (the bigger, the sharper) Default: specular

Material Script: Pass Global attributes –scene_blend How to blend the pass with the existing scene content Flexible version: –Format: scene_blend –Meaning: (pass_result * sourceFactor) + (scene_pixel * destFactor) –Factors: one | zero | src_color | one_minus_src_colour | dest_colour | one_minus_dest_colour | dest_alpha | one_minus_dest_alpha | src_alpha | one_minus_src_alpha –Example: scene_blend one one_minus_dest_alpha Simpler version –Format2: scene_blend –Meaning: »add: 'scene_blend one one‘ (explosions, flares, lights, ghosts) »modulate: 'scene_blend dest_colour zero‘ (darkening, smoked glass) »colour_blend: 'scene_blend src_colour one_minus_src_colour' »alpha_blend: 'scene_blend src_alpha one_minus_src_alpha‘ –Example: scene_blend add –scene_blend_op Specify the operation in scene blending Format: scene_blend_op Meaning: (pass_result * sourceFactor) +(-) (scene_pixel * destFactor) Default: scene_blend_op add

Material Script: Pass Global attributes –Lighting on/off Format: lighting If off, all objects will be fully lit. Default: lighting on –Shading Format: shading Default: shading gouraud –Polygon mode Format: polygon_mode Default: polygon_mode solid

Material Script: Pass Global attributes –Depth check Format: depth_check Default: depth_check on –Depth write Format: depth_write Default: depth_write on –Depth function Determine how to check the depth Format: depth_func –always_fail : Never writes a pixel to the render target –always_pass : Always writes a pixel to the render target –less : Write if (new_Z < existing_Z) –less_equal : Write if (new_Z <= existing_Z) –equal : Write if (new_Z == existing_Z) –not_equal : Write if (new_Z != existing_Z) –greater_equal : Write if (new_Z >= existing_Z) –greater :Write if (new_Z >existing_Z) Default: depth_func less_equal

Material Script: texture_unit Texture –Set name of the texture image Format: texture [ ] [unlimited | numMipMaps] [alpha] [ ] [gamma] Example: texture funkywall.jpg Animated texture –Set the images to be used in animated texture Format1 (short): anim_texture Example: anim_texture flame.jpg Meaning: load 3 frames (frame_0.jpg, frame_1.jpg, frame_2.jpg) for 1.5 sec. Format2 (long): anim_texture... Example: anim_texture flamestart.jpg flamemore.png flameagain.jpg 1.5

Material Script: texture_unit Texture coordinate set –Sets which texture coordinate set is to be used Format: tex_coord_set Example: tex_coord_set 2 Texture address mode –Defines what happens when uv values exceed 1.0 Simple Format: tex_address_mode Extended Format: tex_address_mode Mode: Texture border color –Set the border color when thexture address mode is border Format: tex_border_colour [ ] Example: tex_border_colour

Material Script: texture_unit Color operation –Determines how the color of this texture layer is combined with the one below it –Format: colour_op –Operation types: replace : Replace all color with texture with no adjustment add : Add color components together. modulate : Multiply colour components together alpha_blend : Blend based on texture alpha –Default: colour_op modulate

Material Script: texture_unit Texture Transformation –Scroll Sets a fixed scroll offset for the texture. Format: scroll –Scrolling animation Sets up an animated scroll for the texture layer Format: scroll_anim –Rotate Format: rotate –Rotating animation Format: rotate_anim –Scale Format: scale

Material Script: texture_unit Advanced Texture Transformation –Animation using wave function Format: wave_xform Example: wave_xform scale_x sine xform_types: –scroll_x : Animate the x scroll value –scroll_y : Animate the y scroll value –rotate : Animate the rotate value –scale_x : Animate the x scale value –scale_y : Animate the y scale value wave_types: –sine »A typical sine wave which smoothly loops between min and max values –triangle »An angled wave which increases & decreases at constant speed, changing instantly at the extremes –square »Max for half the wavelength, min for the rest with instant transition between –sawtooth »Gradual steady increase from min to max over the period with an instant return to min at the end. –inverse_sawtooth »Gradual steady decrease from max to min over the period, with an instant return to max at the end. Base: The base value, the minimum if amplitude > 0, the maximum if amplitude < 0

Material Script: other functions There are other advanced shader-based functions in Material script –Vertex/geometry/fragment programs –CG programs –HLSL programs –GLSL programs

Reference for the materials

Manual Creation Using MaterialManager Ogre::MaterialPtr material = Ogre::MaterialManager::getSingleton().create ( "Test/ColourTest", Ogre::ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME ); material->getTechnique(0)->getPass(0)->setDiffuse(Ogre::ColourValue(1.0,0.0,0.0)); Ogre::MaterialPtr material = Ogre::MaterialManager::getSingleton().create ( "Test/ColourTest", Ogre::ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME ); material->getTechnique(0)->getPass(0)->setDiffuse(Ogre::ColourValue(1.0,0.0,0.0));

Material basic attributes ambient reflectance = ColourValue::White (full) diffuse reflectance = ColourValue::White (full) specular reflectance = ColourValue::Black (none) emmissive = ColourValue::Black (none) shininess = 0 (not shiny) No texture layers (& hence no textures) SourceBlendFactor = SBF_ONE, DestBlendFactor = SBF_ZERO (opaque) Depth buffer checking = on Depth buffer writing = on Depth buffer comparison function = CMPF_LESS_EQUAL Culling mode = CULL_CLOCKWISE Ambient lighting in scene = ColourValue(0.5, 0.5, 0.5) (mid-grey) Dynamic lighting = enabled Gourad shading mode Solid polygon mode Bilinear texture filtering