用Ogre做一个效率高又漂亮的水面

以前游戏水面的做法都是用很多张图的序列帧实现的纹理动画，这种固定渲染管线的方式，在最低画质的时候采用特别好，但是对于更高级别的画质，就应该采用更好效果的水面。

水面渲染，Ogre有个插件叫Hydrax，效果很不错，但是效率也低的很，没任何实用价值。只好自己做一个。

一个漂亮3D游戏水面的，一般有水波模拟，bump mapping，倒影，折射，菲捏尔效果，水下效果等，我准备做一些取舍，实现高效率。

1）只保留倒影，去掉折射，菲捏尔效果，水下效果，因为2.5D游戏，视角比较固定，也不需要深入到水下。

2）优化倒影的RTT渲染，手动选择哪些物体需要产生倒影，这样就极大减少渲染批次。

3）bump mapping采用法线贴图方式，计算水面光照。

4）水波模拟适合大海，要和不要关系不大，不同位置的多次采样保证了水纹的流动。

5）用浮点处理水深，提高精度，水深过渡自然。

效果比较满意，水深过渡自然，海水颜色，流动方向，纹理大小等可以动态调节，而且效率上很高，只增加了一个倒影的RTT开销，也不需要美术提供海水图片，shader计算也不复杂。

material FresnelReflectionRefraction
{
	// 一个pass
	technique 
	{
		pass 
		{
			diffuse 0.5 0.5 0.5
			specular 1 1 1 512
			
			scene_blend alpha_blend
			depth_write off  
			
			vertex_program_ref FresnelRefractReflectVP
			{
				param_named_auto worldViewProjMatrix worldviewproj_matrix
				param_named_auto eyePosition camera_position_object_space
				param_named_auto lightPosition1 light_position_object_space 1 
				
				param_named BumpScale float 0.35
				param_named textureScale float2 1 1
				param_named bumpSpeed float2 -0.025 0.025
				param_named_auto time time_0_x 100.0
				param_named waveFreq float 0.028
				param_named waveAmp float 1.8
				
			}
			fragment_program_ref FresnelRefractReflectFP
			{
				param_named_auto ambient ambient_light_colour
				param_named_auto diffuseParameters surface_diffuse_colour
				param_named_auto specularParameters surface_specular_colour
				param_named waterColor float4 0 0.6 0.7 1.0
			}
			// Noise
			texture_unit
			{
				// Perlin noise volume
				texture waves.dds
				// min / mag filtering, no mip
				filtering linear linear none
			}
			// Reflection
			texture_unit Reflection
			{
				// Will be filled in at runtime
				texture Reflection
				tex_address_mode clamp
			}
		}
	}
	
	// 2 个 pass, 高光单独计算不受水深影响, 但高光没法被雾遮挡
	technique
	{
		pass 
		{
			scene_blend alpha_blend
			depth_check on
			depth_write off  
			
			vertex_program_ref FresnelRefractReflectVP
			{
				param_named_auto worldViewProjMatrix worldviewproj_matrix
				param_named_auto eyePosition camera_position_object_space
				param_named_auto lightPosition1 light_position_object_space 1 
				
				param_named BumpScale float 0.2
				param_named textureScale float2 1 1
				param_named bumpSpeed float2 -0.04 0.04
				param_named_auto time time_0_x 100.0
				param_named waveFreq float 0.028
				param_named waveAmp float 1.8
				
			}
			fragment_program_ref FresnelRefractReflectFP_NoSpecular
			{
				param_named_auto ambient ambient_light_colour
				param_named deepColor float4 0 0.3 0.5 1.0
				param_named shallowColor float4 0 1 1 1.0
				param_named reflectionAmount float 1.0
				param_named waterAmount float 0.2
			}
			// Noise
			texture_unit
			{
				// Perlin noise volume
				texture waves.dds
				// min / mag filtering, no mip
				filtering linear linear none
			}
			// Reflection
			texture_unit Reflection
			{
				// Will be filled in at runtime
				texture Reflection
				tex_address_mode clamp
			}
		}
		
		// 高光单独计算,不受水深影响
		pass 
		{
			specular 1 1 1 512
			
			scene_blend add
			depth_write off  
			
			fog_override true
			
			vertex_program_ref FresnelRefractReflectVP
			{
				param_named_auto worldViewProjMatrix worldviewproj_matrix
				param_named_auto eyePosition camera_position_object_space
				param_named_auto lightPosition1 light_position_object_space 1 
				
				param_named BumpScale float 0.2
				param_named textureScale float2 1 1
				param_named bumpSpeed float2 -0.04 0.04
				param_named_auto time time_0_x 100.0
				param_named waveFreq float 0.028
				param_named waveAmp float 1.8
				
			}
			fragment_program_ref FresnelRefractReflectFP_Specular
			{
				param_named_auto specularParameters surface_specular_colour
			}
			// Noise
			texture_unit
			{
				// Perlin noise volume
				texture waves.dds
				// min / mag filtering, no mip
				filtering linear linear none
			}
		}
	}
	
	// 固定管线
	technique
	{
		pass
		{
			ambient 0.588235 0.588235 0.588235 1
			diffuse 0.588235 0.588235 0.588235 1
			specular 0.9 0.9 0.9 20
			scene_blend alpha_blend
			depth_check on
			depth_write off        
			texture_unit
			{
				anim_texture jpg_海湖水.dds 28 2				
			}
			texture_unit
			{
				texture water_depth.tga 1d
				colour_op_ex source1 src_current src_texture
				colour_op_multipass_fallback one zero
				alpha_op_ex modulate src_current src_texture
				tex_coord_set 1
				tex_address_mode clamp
				filtering none none none
			}
		}
	}
}