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[英]OpenGL: how to pass vertex pos from Geometry shader to fragment shader?
[英]How do you move variables from Vertex shader to Geometry shader?
我有以下顶点着色器:
#version 330
layout (location = 0) in ivec4 inOHLC;
layout (location = 1) in int inVolume;
layout (location = 2) in int inTimestamp;
out ivec4 outOHLC;
out int outVolume;
out int outTimestamp;
void main()
{
outOHLC = inOHLC;
outVolume= inVolume;
outTimestamp = inTimestamp;
}
我想在几何着色器中接收outOHLC
、 outVolume
和outTimestamp
。 我这样编码:
#version 330
in ivec4 inOHLC;
in int inVolume;
in int inTimestamp;
layout (line_strip, max_vertices = 2) out;
void main() {
float x = (float)inTimestamp / 100.0;
float y1 = (float)inOHLC[1] / 100.0;
float y2 = (float)inOHLC[1] / 100.0;
gl_Position = vec4(x, y1, 0.0, 0.0);
EmitVertex();
gl_Position = vec4(x, y2, 0.0, 0.0);
EmitVertex();
EndPrimitive();
}
但我收到以下错误:
run:
. . . vertex compilation success.
. . . geometry compilation failed.
Shader Info Log:
ERROR: 7:1: 'inOHLC' : geometry shader input varying variable must be declared as an array
ERROR: 8:1: 'inVolume' : geometry shader input varying variable must be declared as an array
ERROR: 9:1: 'inTimestamp' : geometry shader input varying variable must be declared as an array
ERROR: 15:1: ')' : syntax error syntax error
在@Rabbid76 评论之后,我将代码修改如下:
#version 330
in ivec4 ohlc[];
in int volume[];
in int timestamp[];
layout (line_strip, max_vertices = 2) out;
void main()
{
float x = (float)timestamp / 100.0;
float y1 = (float)ohlc[1] / 100.0;
float y2 = (float)ohlc[2] / 100.0;
gl_Position = vec4(x, y1, 0.0, 0.0);
EmitVertex();
gl_Position = vec4(x, y2, 0.0, 0.0);
EmitVertex();
EndPrimitive();
}
现在我只得到一个错误:
run:
. . . vertex compilation success.
. . . geometry compilation failed.
Shader Info Log:
ERROR: 40:1: ')' : syntax error syntax error
我猜这与(float)
cast(它甚至存在于 GLSL 中吗?)或浮点变量定义有关。
仔细阅读消息:
几何着色器输入变量必须声明为数组
几何着色器的输入是一个图元。 这意味着构成图元的顶点着色器的所有输出都是组合的。 因此几何着色器的输入是 arrays:
in ivec4 inOHLC[];
in int inVolume[];
in int inTimestamp[];
此外,您必须为几何着色器指定输入图元类型。 例如一行:
layout(lines) in;
原始类型lines
意味着几何着色器接收 2 个顶点(输入的数组大小为 2)。
GLSL 没有像 C 这样的转换运算符。 如果要将int
转换为float
,则必须构造一个新的float
。 重载的float
构造函数接受一个int
参数:
float y1 = (float)ohlc[1] / 100.0;
float y1 = float(ohlc[1]) / 100.0;
Indices start at 0 not at 1 (like in C, C++, C#, Java, JavaScript, Python, ...):
float y1 = float(ohlc[0]) / 100.0;
float y2 = float(ohlc[1]) / 100.0;
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