Examples of multipass rendering techniques include:.Postprocessing rendered pixels. To create effects such as color grading and displacement mapping, define techniques that use as input the color buffer rendered by SceneKit and process that buffer with a fragment shader.Deferred shading. To create effects such as motion blur and screen-space ambient occlusion (SSAO), define techniques that capture information about the scene into an intermediary buffer during the main rendering pass and then perform additional drawing passes using that buffer to create the final output image. The figure below illustrates the rendering process for an SSAO technique.Figure 1.

Example of a multipass techniqueTo create an SCNTechnique object, you supply a technique definition that specifies the input and output image buffers, shader programs, shader input variables, and rendering options for each drawing pass in the technique. Defining a technique does not require Metal or OpenGL client code, but you should be familiar with the terminology and conventions of GPU rendering.To use a technique, assign it to the property of a view (or other SceneKit renderer object) or a camera. Defining a Technique. SceneKit treats rendering techniques—along with shaders, 3D models, and 2D art assets—as resources rather than as part of your application code. Because the effects you create with techniques are highly visual, this approach allows you to separate design efforts from development efforts and quickly iterate on creating the visual content of your app or game.Create a technique object using the method, providing a dictionary that defines the technique as a series of drawing passes, each with its own shader program, inputs and outputs, and rendering options.

Typically, you obtain this dictionary from a property list file included in your app’s bundle resources. Table 1 and the additional tables and sections that follow specify the format of this dictionary’s contents. KeyValuepassesA dictionary of drawing pass definitions.Each key is a unique string you provide to identify the pass, and the corresponding value is a dictionary defining that drawing pass. See.sequenceAn array of strings, each of which names a drawing pass from the passes dictionary. SceneKit performs the drawing passes in the order specified by this array.symbolsA dictionary defining the bindings for GLSL attributes and uniform variables used in the technique’s shader programs.Each key matches the name of a symbol used in the shader source code, and the corresponding value is a dictionary describing how that symbol should be used.

See.targets (optional)A dictionary defining intermediary rendering targets.Each key is a unique string you provide to identify the target (used in the inputs and outputs dictionaries of a drawing pass definition), and the corresponding value is a dictionary defining the rendering target. KeyTypeValuedrawStringWhat to render for the drawing pass:DRAW SCENE: Render the entire scene.DRAW NODE: Render only the node specified by the node key (and its hierarchy of child nodes).DRAW QUAD: Render only a rectangle covering the entire bounds of the view. Use this option for drawing passes that process image buffers output by earlier passes.programStringThe GLSL shader program to use for the drawing pass.Shader source code files in the app’s bundle resources directory must have the same base name and the extensions.vsh (vertex shader) and.fsh (fragment shader). For example, if the program name is “invert”, the files “invert.fsh” and “invert.vsh” must exist.metal Vertex Shadermetal Fragment ShaderStringThe names of the Metal vertex and fragment shader functions to use for the drawing pass. These functions must exist in the app’s default Metal library.You must specify both fragment and vertex shaders, and you must specify either a GLSL shader program, a pair of Metal functions, or both. If both are specified, SceneKit uses whichever shader is appropriate for the current renderer.inputsDictionaryDefinitions of input variables for the drawing pass.Each key is the name of a uniform variable used in the GLSL shader source code referenced by the program key.

The corresponding value may be any of:A symbol name from the technique’s symbols dictionaryA render target name (see )A dictionary describing a texture sampler (see )outputsDictionaryDefinitions of output image buffers for the drawing pass.Each key is one of the strings color, depth, or stencil, and the corresponding value is a string identifying a render target. See.node (optional)StringThe property of the node to render, or self to reference the node the technique is attached to. Applies only if the draw key specifies DRAW NODE.color States (optional)DictionaryOptions for the color output; one or more of these keys and values:clear (Boolean, defaults to false in macOS and true on iOS): Whether to clear the rendering target before drawing. If true, you must specify one of the clear Color and clear With Scene Background Color options.clear Color (string): The color to fill the render target with when clearing, specified in floating-point RGBA format. KeyTypeValuesemanticStringUse this option to bind shader symbols to data supplied by SceneKit:The values vertex, normal, color, and texcoord bind to geometry source semantics. See Geometry Semantic Identifiers.The values model View Projection Transform, model View Transform, model Transform, view Transform, projection Transform, normal Transform, model View Projection Inverse Transform, model View Inverse Transform, model Inverse Transform, view Inverse Transform, projection Inverse Transform, and normal Inverse Transform bind to rendering transformation matrices. See Rendering Transform Keys.The value time binds the system time elapsed since rendering began.If you set a semantic value for a symbol, no type value is required.typeStringThe GLSL type of the input variable: float, vec2, vec3, vec4, mat4, int, ivec2, ivec3, ivec4, mat3, sampler2D, or none.Use this option when providing custom values to shader programs (see ).image (optional)StringIf the symbol’s type is sampler2D, the name of an image file in the app’s bundle resources directory.Category Masks.

Minecraft shaders are a simple way to modify the way Minecraft renders its lighting and shadows to create the desired effect. Check out our lists of the best Minecraft mods and best Minecraft seeds if you want to get more from the game. First, we'll teach you how to install shaders in Minecraft.

When SceneKit performs a rendering pass whose draw option is DRAW SCENE or DRAW NODE, you can use category masks to filter the set of nodes drawn during that pass. For each node in the scene (or for DRAW NODE, in the node subtree), SceneKit compares the node’s property and the include Category Mask and exclude Category Mask options in the pass definition using bitwise AND operations. If the node’s category mask and the include mask overlap (that is, the bitwise AND results in a nonzero value) and the node’s category mask and the exclude mask do not overlap, SceneKit includes the node in the drawing pass. Otherwise the node is not rendered in the pass. Render Targets, Inputs and Outputs. A drawing pass renders pixel data into one or more target image buffer (or framebuffer).

In SceneKit’s main drawing pass, the color render target is the screen (or rather, a view or layer for screen display), and a depth render target temporarily stores the information needed to ensure that rendered surfaces appear in the correct depth order.A pass in a custom rendering technique may postprocess the pixel data in SceneKit’s render target, generate its own pixel data for display, or render to an intermediate target to be used as input in a later pass. You specify render targets using the following identifiers in the inputs and outputs dictionaries of a pass definition:.Use the COLOR and DEPTH targets as inputs to identify the color and depth buffers rendered to in SceneKit’s main drawing pass.Use the COLOR target as an output to identify the image buffer displayed as the end result of a technique.To create an intermediate target, define your own identifier as a key in the targets dictionary of a technique definition. For the corresponding value, provide a dictionary defining the render target using the keys and values in.

Intermediate targets may be color, depth, or combined depth and stencil buffers. After you define a target, you can use its identifier in the inputs and outputs dictionaries of a pass definition.To use an image as an input texture for a pass, define a symbol of type sampler2D in the technique’s symbols dictionary.To specify a render target or image sampler in the inputs dictionary of a pass definition, you can provide either an identifier string or a dictionary with the format described in. The options for samplers correspond to similar properties for SceneKit material textures. For more details on each, see.

KeyTypeValuetypeStringThe type of render target: color, depth, or stencil.format (optional)StringThe render target’s pixel format; one of the following:Color: rgba (default), rgb32f, r8, or r16Depth/stencil: depth24 (default) or depth24stencil8sizeStringThe size of the render target image, in points, specified in a string of format “WxH”. For example, the string “320x480” specifies an image buffer 320 points wide by 480 points tall.scale Factor (optional)Number (floating-point)The scale factor of the render target. Defaults to 1.0. For example, a value of 2.0 specifies 2 pixels per point, so a target whose size is “320x480” is 640 by 960 pixels.Table 6.

The blend States key of a pass definition defines color blending options. Blending is disabled by default for faster rendering performance. Including a dictionary for this key enables blending (unless the dictionary’s enable key specifies false).