根据Apple的文档,您可以使用NSColor,NSImage和CALayer为SCNMaterialProperty提供纹理。SCNMaterialProperty
但是,我想知道是否有一种方法可以提供现有的OpenGL纹理,该纹理已使用glGenTextures创建并单独渲染。
我当然可以读取纹理的缓冲区,设置一个NSImage,并将该缓冲区提供给SCNMaterialProperty;但出于性能原因,这显然不是最佳的。
通过覆盖我猜材料的着色器程序来实现上述内容是有意义的,但执行此操作的文档似乎不存在。
您可以通过创建为材质分配 SCNProgram 来覆盖着色器程序。然后,在 SCNProgramDelegate
的委托方法之一中,您可以绑定自己的纹理(和其他制服)值。但是,您必须编写自己的着色器。
如果你习惯了Objective-C,有一些设置,但当你想到相应的OpenGL代码时,它真的没有那么多。
下面是将纹理绑定到几何对象表面的示例着色器程序。为简单起见,它不会对法线和光源进行任何着色。
请注意,我不知道您想如何绑定您的特定纹理,因此在下面的代码中,我使用 GLKit 读取了一个 png 并使用该纹理。
// Create a material
SCNMaterial *material = [SCNMaterial material];
// Create a program
SCNProgram *program = [SCNProgram program];
// Read the shader files from your bundle
NSURL *vertexShaderURL = [[NSBundle mainBundle] URLForResource:@"yourShader" withExtension:@"vert"];
NSURL *fragmentShaderURL = [[NSBundle mainBundle] URLForResource:@"yourShader" withExtension:@"frag"];
NSString *vertexShader = [[NSString alloc] initWithContentsOfURL:vertexShaderURL
encoding:NSUTF8StringEncoding
error:NULL];
NSString *fragmentShader = [[NSString alloc] initWithContentsOfURL:fragmentShaderURL
encoding:NSUTF8StringEncoding
error:NULL];
// Assign the shades
program.vertexShader = vertexShader;
program.fragmentShader = fragmentShader;
// Bind the position of the geometry and the model view projection
// you would do the same for other geometry properties like normals
// and other geometry properties/transforms.
//
// The attributes and uniforms in the shaders are defined as:
// attribute vec4 position;
// attribute vec2 textureCoordinate;
// uniform mat4 modelViewProjection;
[program setSemantic:SCNGeometrySourceSemanticVertex
forSymbol:@"position"
options:nil];
[program setSemantic:SCNGeometrySourceSemanticTexcoord
forSymbol:@"textureCoordinate"
options:nil];
[program setSemantic:SCNModelViewProjectionTransform
forSymbol:@"modelViewProjection"
options:nil];
// Become the program delegate so that you get the binding callback
program.delegate = self;
// Set program on geometry
material.program = program;
yourGeometry.materials = @[material];
在此示例中,着色器编写为
// yourShader.vert
attribute vec4 position;
attribute vec2 textureCoordinate;
uniform mat4 modelViewProjection;
varying vec2 texCoord;
void main(void) {
// Pass along to the fragment shader
texCoord = textureCoordinate;
// output the projected position
gl_Position = modelViewProjection * position;
}
和
// yourShader.frag
uniform sampler2D yourTexture;
varying vec2 texCoord;
void main(void) {
gl_FragColor = texture2D(yourTexture, texCoord);
}
最后实现...bindValueForSymbol:...
方法将纹理绑定到"yourTexture"制服。
- (BOOL) program:(SCNProgram *)program
bindValueForSymbol:(NSString *)symbol
atLocation:(unsigned int)location
programID:(unsigned int)programID
renderer:(SCNRenderer *)renderer
{
if ([symbol isEqualToString:@"yourTexture"]) {
// I'm loading a png with GLKit but you can do your very own thing
// here to bind your own texture.
NSError *error = nil;
NSString *imagePath = [[NSBundle mainBundle] pathForResource:@"sampleImage" ofType:@"png"];
GLKTextureInfo *texture = [GLKTextureLoader textureWithContentsOfFile:imagePath options:nil error:&error];
if(!texture) {
NSLog(@"Error loading file: %@", [error localizedDescription]);
}
glBindTexture(GL_TEXTURE_2D, texture.name);
return YES; // indicate that the symbol was bound successfully.
}
return NO; // no symbol was bound.
}
此外,出于调试目的,实现program:handleError:
以打印出任何着色器编译错误非常有帮助
- (void)program:(SCNProgram*)program handleError:(NSError*)error {
// Log the shader compilation error
NSLog(@"%@", error);
}
如果你需要直接处理OpenGL并绑定你的自定义纹理,那么SCNProgram或SCNNode的委托是要走的路(MountainLion或更高版本)。如果您有 Apple 开发人员帐户,您将在此处找到示例代码:http://developer.apple.com/downloads/在"WWDC 2013 示例代码"下。 查找"OS_X_SceneKit_Slides_WWDC2013"