对不起，这需要一点解释。我正在努力使它尽可能简单。
我想做的事：我正在可视化高度场。高度字段可能有多个补丁。面片是一种较小的纹理，可以改变高度场。
我使用的是OpenGL 4.0，主要是镶嵌着色器。然而，对于这个问题，这应该是无关紧要的。
一切就绪我有高度场的可视化(没有补丁(工作。与该问题相关的主要部分是镶嵌评估着色器和片段着色器。
镶嵌评估着色器从高度场采样器获取每个顶点的高度。
layout(quads, fractional_odd_spacing, ccw) in;
out float onEdge;
out float teDistanceToMinHeight;
out vec4 tcPosition;
void main()
{
// bilinear interpolate: position
vec4 pos_a = mix(gl_in[0].gl_Position, gl_in[1].gl_Position, gl_TessCoord.x);
vec4 pos_b = mix(gl_in[3].gl_Position, gl_in[2].gl_Position, gl_TessCoord.x);
vec4 position = mix(pos_a, pos_b, gl_TessCoord.y);
// bilinear interpolate: hf texture coordinate
vec2 tex_a = mix(gl_in[0].gl_TexCoord[HFTexCoordID].xy, gl_in[1].gl_TexCoord[HFTexCoordID].xy, gl_TessCoord.x);
vec2 tex_b = mix(gl_in[3].gl_TexCoord[HFTexCoordID].xy, gl_in[2].gl_TexCoord[HFTexCoordID].xy, gl_TessCoord.x);
vec2 hfTexCoord = mix(tex_a, tex_b, gl_TessCoord.y);
float height = getHeightFieldHeight(hfTexCoord);
position.y = height;
//position.y = getHeightFieldHeightMin();
gl_Position = gl_ModelViewProjectionMatrix * position;
tcPosition = gl_Position;
gl_TexCoord[HFTexCoordID].xy = hfTexCoord;
// a vertex is on the edge of a patch if one of the tess coords is 0
onEdge = float((gl_TessCoord.x == 0 || gl_TessCoord.y == 0));
teDistanceToMinHeight = height - getHeightFieldHeightMin();
}
片段着色器使用属于手头片段的顶点的创建高度来访问1D高度palett纹理。请暂时忽略高度梯度。它用于计算法线。这完全可以。
in float onEdge;
in float teDistanceToMinHeight;
in vec4 tcPosition;
out vec4 FragColor;
vec3
getHeightMapGradient(in vec2 ts_position,
in vec2 texel_offset)
{
vec3 x = vec3(2.0 * texel_offset.x, 0.0, getHeightFieldHeight(ts_position + vec2(texel_offset.x, 0.0))
- getHeightFieldHeight(ts_position - vec2(texel_offset.x, 0.0)));
vec3 y = vec3(0.0, 2.0 * texel_offset.y, getHeightFieldHeight(ts_position + vec2(0.0, texel_offset.y))
- getHeightFieldHeight(ts_position - vec2(0.0, texel_offset.y)));
return cross(x, y);
}
void main()
{
if(teDistanceToMinHeight < 0.00001){
// filter points near the zero position
discard;
}
// attributes
vec2 hfTexCoords = gl_TexCoord[HFTexCoordID].xy;
//float hfPaletteTexCoord = getHeightFieldHeight(hfTexCoords) / HeightFieldHeight;
float hfPaletteTexCoord = (texture(HeightField, hfTexCoords).r -HeightFieldLowering);
vec2 heightMapSize = vec2(textureSize(HeightField, 0).xy);
vec2 heightMapTexelSize = vec2(1.0) / vec2(heightMapSize);
// some standard colors
vec4 white = vec4(1);
vec4 yellow = vec4(1,1,0,1);
vec4 blue = vec4(0,0,1,1);
// get the color
FragColor = texture(HeightFieldPalette, hfPaletteTexCoord ); // use height field palette as color
if(onEdge > 0.9 && ShowOriginalGrid == 1 ){
FragColor = mix(FragColor, yellow, 0.5);
}
// shading
vec3 n = normalize(getHeightMapGradient(hfTexCoords, heightMapTexelSize).xzy);
vec3 l = vec3(1,1,0);
vec3 v = normalize(CameraPosition - tcPosition.xyz);
vec3 h = normalize(l + v);
float df= dot(n, l);
FragColor = (FragColor * (df * 0.5 + 0.5)) // diffuse
+ vec4(1) * pow(max(0.0, dot(n,h)), 60.0) // specular
+ 0.1; // ambient
}
包含在每个着色器之前的是以下代码。它主要包含所有统一函数和辅助函数。
#version 400 compatibility
// defines
#define HFTexCoordID 0
// environment
uniform ivec2 ScreenSize = ivec2(800,600);
uniform vec3 CameraPosition = vec3(0);
// tesselation
uniform float MaxEdgeLength = 4;
// height field
uniform float HeightFieldHeight = 1;
uniform float HeightFieldLowering = 0.2;
uniform sampler2D HeightField;
uniform sampler1D HeightFieldPalette;
// density map
uniform sampler2D DensityMap;
// patches
uniform sampler2D[20] Patches;
uniform int PatchesCount = 0;
uniform ivec2[20] PatchesPositions;
uniform float[20] PatchesHeights;
uniform ivec2[20] PatchesSizes;
// show options
uniform int ShowOriginalGrid = 0;
// functions
ivec2 getHFPosition(vec2 hfTexCoords){
return ivec2(textureSize(HeightField, 0).xy * hfTexCoords);
}
ivec2 getPatchSize(in int patchIndex){
return PatchesSizes[patchIndex];
//return textureSize(Patches[patchIndex], 0).xy;
}
vec2 toPatchCoords(in int patchIndex, in vec2 hfTexCoords){
ivec2 hfPosition = getHFPosition(hfTexCoords);
ivec2 patchStart = PatchesPositions[patchIndex];
ivec2 patchPos = hfPosition - patchStart;
//return textureSize(Patches[1], 0).xy;
return vec2(patchPos / getPatchSize(patchIndex));
}
float getPatchHeight(in int patchIndex, in vec2 hfTexCoords){
vec2 patchCoords = toPatchCoords(patchIndex, hfTexCoords);
// seams like the combination of the for loop with this
// texture access results in undefined behavior.
float relHeight = (texture(Patches[patchIndex], patchCoords).r -0.5);
return relHeight * PatchesHeights[patchIndex] * HeightFieldHeight;
}
float getPatchedHeight(in vec2 texCoords){
float patchesHeight = 0;
// working
//patchesHeight += getPatchHeight(0, texCoords);
//patchesHeight += getPatchHeight(1, texCoords);
//patchesHeight += getPatchHeight(2, texCoords);
// only works for i < 5 .
for(int i = 0; i < 6 && i < PatchesCount-1; i++){
patchesHeight += getPatchHeight(i, texCoords);
}
return patchesHeight;
}
float getHeightFieldHeight(in vec2 textureCoordinates){
float height = (texture(HeightField, textureCoordinates).r -HeightFieldLowering) * HeightFieldHeight;
height += getPatchedHeight(textureCoordinates);
return height;
}
float getHeightFieldHeightMin(){
return (-0.2 * HeightFieldHeight);
}
float getDensity(in vec2 coords){
return texture(DensityMap, coords).r;
}
问题
只要我不访问Patches制服，上面描述和粘贴的着色器都可以正常工作。
uniform sampler2D[20] Patches;
sampler2D[]背后的想法是拥有一种数组，而该数组的每个纹理可能具有不同的大小。我知道每个构造都使用(在本例中(20个纹理单元。这种罚款限制。
访问Patches uniform时，片段着色器仅输出黑色像素。镶嵌评估着色器工作正常，我知道，因为我可以在高度场中看到山丘，这不是它的一部分。
我非常感谢你的建议。关于这个问题。
我知道我可以使用sampler2DArray，但每个元素(纹理(必须具有相同的大小。但我需要补丁的大小是可伸缩的。将补丁切割成固定大小的纹理，并在着色器中将它们重新缝合在一起，这可能是一种替代方案，但我不想实现这种组织开销，除非我真的必须这样做。
信息日志
Visualization Lib
rary v2011.5.1142 [f32]
Jun 9 2011 - 11:36:25 - GCC compiler [RELEASE] [x32]
--- Environment ---
VL_LOGFILE_PATH <not present>
VL_DATA_PATH <not present>
VL_VERBOSITY_LEVEL = NORMAL
VL_CHECK_GL_STATES = YES
--- Global Settings ---
Log file = log.txt
Data path = ../data
Verbosity level = NORMAL
Check OpenGL States = YES
--- GLEW ---
GLEW version: 1.5.7
--- OpenGL Info ---
OpenGL version: 4.1.0 NVIDIA 260.19.21
OpenGL vendor: NVIDIA Corporation
OpenGL renderer: Quadro 6000/PCI/SSE2
OpenGL profile: Compatible
GLSL version: 4.10 NVIDIA via Cg compiler
Max texture size: 16384
Texture coords: 8
Texture conventional units: 4
Texture image units: 32
Anisotropic texture filter: YES, 16X
S3 Texture Compression: YES
Vertex Buffer Object: YES
Pixel Buffer Object: YES
Framebuffer Object: YES
Max vertex attributes: 16
Max varying floats: 60
Max fragment uniform components: 2048
Max vertex uniform components: 4096
Max elements vertices: 1048576
Max elements indices: 1048576
--- OpenGL Extensions ---
GL_ARB_blend_func_extended GL_ARB_color_buffer_float
GL_ARB_compatibility GL_ARB_copy_buffer
GL_ARB_depth_buffer_float GL_ARB_depth_clamp
GL_ARB_depth_texture GL_ARB_draw_buffers
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GL_ARB_ES2_compatibility GL_ARB_explicit_attrib_location
GL_ARB_fragment_coord_conventions GL_ARB_fragment_program
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GL_EXT_geometry_shader4 GL_EXT_gpu_program_parameters
GL_EXT_gpu_shader4 GL_EXT_multi_draw_arrays
GL_EXT_packed_depth_stencil GL_EXT_packed_float
GL_EXT_packed_pixels GL_EXT_pixel_buffer_object
GL_EXT_point_parameters GL_EXT_provoking_vertex
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GL_EXT_separate_shader_objects GL_EXT_separate_specular_color
GL_EXT_shader_image_load_store GL_EXT_shadow_funcs
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GL_IBM_rasterpos_clip GL_IBM_texture_mirrored_repeat
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GL_NV_texture_multisample GL_NV_texture_rectangle
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GL_NV_vertex_array_range GL_NV_vertex_array_range2
GL_NV_vertex_attrib_integer_64bit GL_NV_vertex_buffer_unified_memory
GL_NV_vertex_program GL_NV_vertex_program1_1
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GL_NV_vertex_program3 GL_NV_video_capture
GL_NVX_conditional_render GL_NVX_gpu_memory_info
GL_SGIS_generate_mipmap GL_SGIS_texture_lod
GL_SGIX_depth_texture GL_SGIX_shadow
GL_SUN_slice_accum
--- GLEW ---
GLEW version: 1.5.7
--- OpenGL Info ---
OpenGL version: 4.1.0 NVIDIA 260.19.21
OpenGL vendor: NVIDIA Corporation
OpenGL renderer: Quadro 6000/PCI/SSE2
OpenGL profile: Compatible
GLSL version: 4.10 NVIDIA via Cg compiler
Max texture size: 16384
Texture coords: 8
Texture conventional units: 4
Texture image units: 32
Anisotropic texture filter: YES, 16X
S3 Texture Compression: YES
Vertex Buffer Object: YES
Pixel Buffer Object: YES
Framebuffer Object: YES
Max vertex attributes: 16
Max varying floats: 60
Max fragment uniform components: 2048
Max vertex uniform components: 4096
Max elements vertices: 1048576
Max elements indices: 1048576
--- OpenGL Extensions ---
GL_ARB_blend_func_extended GL_ARB_color_buffer_float
GL_ARB_compatibility GL_ARB_copy_buffer
GL_ARB_depth_buffer_float GL_ARB_depth_clamp
GL_ARB_depth_texture GL_ARB_draw_buffers
GL_ARB_draw_buffers_blend GL_ARB_draw_indirect
GL_ARB_draw_elements_base_vertex GL_ARB_draw_instanced
GL_ARB_ES2_compatibility GL_ARB_explicit_attrib_location
GL_ARB_fragment_coord_conventions GL_ARB_fragment_program
GL_ARB_fragment_program_shadow GL_ARB_fragment_shader
GL_ARB_framebuffer_object GL_ARB_framebuffer_sRGB
GL_ARB_geometry_shader4 GL_ARB_get_program_binary
GL_ARB_gpu_shader5 GL_ARB_gpu_shader_fp64
GL_ARB_half_float_pixel GL_ARB_half_float_vertex
GL_ARB_imaging GL_ARB_instanced_arrays
GL_ARB_map_buffer_range GL_ARB_multisample
GL_ARB_multitexture GL_ARB_occlusion_query
GL_ARB_occlusion_query2 GL_ARB_pixel_buffer_object
GL_ARB_point_parameters GL_ARB_point_sprite
GL_ARB_provoking_vertex GL_ARB_robustness
GL_ARB_sample_shading GL_ARB_sampler_objects
GL_ARB_seamless_cube_map GL_ARB_separate_shader_objects
GL_ARB_shader_bit_encoding GL_ARB_shader_objects
GL_ARB_shader_precision GL_ARB_shader_subroutine
GL_ARB_shading_language_100 GL_ARB_shadow
GL_ARB_sync GL_ARB_tessellation_shader
GL_ARB_texture_border_clamp GL_ARB_texture_buffer_object
GL_ARB_texture_buffer_object_rgb32 GL_ARB_texture_compression
GL_ARB_texture_compression_bptc GL_ARB_texture_compression_rgtc
GL_ARB_texture_cube_map GL_ARB_texture_cube_map_array
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GL_EXT_bgra GL_EXT_bindable_uniform
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GL_EXT_blend_subtract GL_EXT_compiled_vertex_array
GL_EXT_Cg_shader GL_EXT_depth_bounds_test
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GL_EXT_draw_instanced GL_EXT_draw_range_elements
GL_EXT_fog_coord GL_EXT_framebuffer_blit
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GL_EXT_geometry_shader4 GL_EXT_gpu_program_parameters
GL_EXT_gpu_shader4 GL_EXT_multi_draw_arrays
GL_EXT_packed_depth_stencil GL_EXT_packed_float
GL_EXT_packed_pixels GL_EXT_pixel_buffer_object
GL_EXT_point_parameters GL_EXT_provoking_vertex
GL_EXT_rescale_normal GL_EXT_secondary_color
GL_EXT_separate_shader_objects GL_EXT_separate_specular_color
GL_EXT_shader_image_load_store GL_EXT_shadow_funcs
GL_EXT_stencil_two_side GL_EXT_stencil_wrap
GL_EXT_texture3D GL_EXT_texture_array
GL_EXT_texture_buffer_object GL_EXT_texture_compression_latc
GL_EXT_texture_compression_rgtc GL_EXT_texture_compression_s3tc
GL_EXT_texture_cube_map GL_EXT_texture_edge_clamp
GL_EXT_texture_env_combine GL_EXT_texture_env_dot3
GL_EXT_texture_filter_anisotropic GL_EXT_texture_integer
GL_EXT_texture_lod GL_EXT_texture_lod_bias
GL_EXT_texture_mirror_clamp GL_EXT_texture_object
GL_EXT_texture_shared_exponent GL_EXT_texture_sRGB
GL_EXT_texture_swizzle GL_EXT_timer_query
GL_EXT_transform_feedback2 GL_EXT_vertex_array
GL_EXT_vertex_array_bgra GL_EXT_vertex_attrib_64bit
GL_IBM_rasterpos_clip GL_IBM_texture_mirrored_repeat
GL_KTX_buffer_region GL_NV_blend_square
GL_NV_conditional_render GL_NV_copy_depth_to_color
GL_NV_copy_image GL_NV_depth_buffer_float
GL_NV_depth_clamp GL_NV_explicit_multisample
GL_NV_fence GL_NV_float_buffer
GL_NV_fog_distance GL_NV_fragment_program
GL_NV_fragment_program_option GL_NV_fragment_program2
GL_NV_framebuffer_multisample_coverage GL_NV_geometry_shader4
GL_NV_gpu_program4 GL_NV_gpu_program4_1
GL_NV_gpu_program5 GL_NV_gpu_program_fp64
GL_NV_gpu_shader5 GL_NV_half_float
GL_NV_light_max_exponent GL_NV_multisample_coverage
GL_NV_multisample_filter_hint GL_NV_occlusion_query
GL_NV_packed_depth_stencil GL_NV_parameter_buffer_object
GL_NV_parameter_buffer_object2 GL_NV_pixel_data_range
GL_NV_point_sprite GL_NV_primitive_restart
GL_NV_register_combiners GL_NV_register_combiners2
GL_NV_shader_buffer_load GL_NV_texgen_reflection
GL_NV_texture_barrier GL_NV_texture_compression_vtc
GL_NV_texture_env_combine4 GL_NV_texture_expand_normal
GL_NV_texture_multisample GL_NV_texture_rectangle
GL_NV_texture_shader GL_NV_texture_shader2
GL_NV_texture_shader3 GL_NV_transform_feedback
GL_NV_transform_feedback2 GL_NV_vdpau_interop
GL_NV_vertex_array_range GL_NV_vertex_array_range2
GL_NV_vertex_attrib_integer_64bit GL_NV_vertex_buffer_unified_memory
GL_NV_vertex_program GL_NV_vertex_program1_1
GL_NV_vertex_program2 GL_NV_vertex_program2_option
GL_NV_vertex_program3 GL_NV_video_capture
GL_NVX_conditional_render GL_NVX_gpu_memory_info
GL_SGIS_generate_mipmap GL_SGIS_texture_lod
GL_SGIX_depth_texture GL_SGIX_shadow
GL_SUN_slice_accum
PatchesContainer::PatchesContainer: working dir: ./data/patches/pick_height_testing_png/
PatchesContainer::loadPatchesFromWorkingDir ignoring file = data/patches/pick_height_testing_png/.svn
Patch::initialize(): name = data/patches/pick_height_testing_png/patch01-position=20x20-maxHeight=1.0.png
width = 50
height = 50
depth = 0
format = IF_LUMINANCE
type = IT_UNSIGNED_BYTE
pitch = 50
bytealign = 1
Patch::initialize(): name = data/patches/pick_height_testing_png/patch02-position=20x2-maxHeight=1.5.png
width = 20
height = 20
depth = 0
format = IF_LUMINANCE
type = IT_UNSIGNED_BYTE
pitch = 20
bytealign = 1
Found matching densitymap ./data/density_maps/pick_height_testing_png.png
loading height field image
name = ./data/horizons/pick_height_testing.png
width = 200
height = 200
depth = 0
format = IF_LUMINANCE
type = IT_UNSIGNED_BYTE
pitch = 200
bytealign = 1
name = ./data/textures/tesselation_palette_blue_red.png
width = 300
height = 0
depth = 0
format = IF_RGB
type = IT_UNSIGNED_BYTE
pitch = 900
bytealign = 1
GL_MAX_TESS_EVALUATION_TEXTURE_IMAGE_UNITS: 32
好吧，我可以看到一个问题：
均匀sampler2D[20]补丁；
我将冒险猜测，您的OpenGL 4.0级硬件无法在一个着色器阶段内使用超过16个纹理。如果要对此进行验证，请选中GL_MAX_TESS_EVALUATION_TEXTURE_IMAGE_UNITS；我敢打赌是16。
此外，访问采样器数组的规则非常严格(我敢打赌你违反了这些规则(。在GLSL 4.00中，采样器阵列的索引必须为：
1：编译时间常数表达式
2：解析为统一值的表达式。不是关键字中的uniform，而是基于编译时常数或统一值的表达式。它们不能基于从纹理、着色器阶段输入或任何类似内容中检索到的值。
这是合法的：
for(int i = 0; i < someUniform; i++)
{
texture(Patches[i], texCoord);
}
这是不合法：
texture(Patches[positionOfSomeVertex * uniformScaleFactor], texCoord);
人们使用数组纹理而不是采样器数组是有原因的。
Adendum：也许引用GLSL版本4.10规范会有所帮助：
片段着色器表达式是如果所有片段都是动态一致的评估它会得到相同的结果价值当涉及循环时指的表达式值相同的循环迭代。什么时候涉及功能，这指的是来自同一呼叫点的呼叫。
对于其他着色器阶段，基于他们处理的每个实例的数据。
请注意，常量表达式是琐碎的动态统一。它遵循典型的循环计数器基于这些也是动态的制服
您的表达式包含一个基于不动态统一的东西的条件分支。因此，所使用的索引不是动态统一的。
"动态一致"的基本思想是：给定相同的uniform值，我应该能够传递任何作为着色器阶段输入，并且将从数组访问相同的纹理。您的代码不能保证这一点。