OpenGL How to get gl_Position.w ?

This topic is 1800 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

Recommended Posts

I copied the OpenGL ES 2.0 style of specifying vertices with an "attribute vec4 position;" along with other things (is this how it's supposed to be done in OpenGL 4?).

But now my shadow mapping is messed up as the shadows aren't effected by the camera's rotation/movement.

I think it might be caused by the w component of "position" not matching what it would be in gl_Position.

What should I be setting the w component to?

attribute vec4 position;

uniform mat4 projection;
uniform mat4 model;
uniform mat4 view;
uniform mat4 modelViewInv;

uniform mat4 lightMatrix;
uniform vec3 lightPos;
uniform vec3 lightDir;

varying vec4 lpos;

attribute vec3 normalIn;
varying vec3 normalOut;

attribute vec2 texCoordIn0;
varying vec2 texCoordOut0;

void main(void)
{
vec4 vpos = (view * (model * position));
lpos = lightMatrix * vpos;
gl_Position = projection * (view * (model * position));

vec3 normalEyeSpace = vec3( modelViewInv * vec4(normalIn, 0.0) );
normalOut = normalize(normalEyeSpace);

texCoordOut0 = texCoordIn0;
}




uniform vec4 color;

uniform sampler2D texture0;

varying vec4 lpos;

varying vec2 texCoordOut0;

void main (void)
{
vec3 smcoord = lpos.xyz / lpos.w;

vec4 texColor = texture2D(texture0, texCoordOut0);

gl_FragColor = vec4(color.xyz * texColor.xyz * shadow, color.w * texColor.w);
}



Share on other sites

What should I be setting the w component to?

1 (the projection matrix will take care about the rest)

Share on other sites

Never mind, got it working.

Share on other sites

I think varying is deprecated. Don't take my word for that though.

Share on other sites

I think varying is deprecated. Don't take my word for that though.

All uniform, varying and attribute were removed and instead in, out and inout are used. The problem is that GL < 3 only supports the former, while GL >= 3 only supports the latter (compatibility profile aside), unless I misunderstood something, so what keywords you use depends on how much old hardware do you pretend to support.

• Similar Content

• By xhcao
Does sync be needed to read texture content after access texture image in compute shader?
My simple code is as below,
glUseProgram(program.get());
glBindImageTexture(0, texture[0], 0, GL_FALSE, 3, GL_READ_ONLY, GL_R32UI);
glBindImageTexture(1, texture[1], 0, GL_FALSE, 4, GL_WRITE_ONLY, GL_R32UI);
glDispatchCompute(1, 1, 1);
// Does sync be needed here?
glUseProgram(0);
GL_TEXTURE_CUBE_MAP_POSITIVE_X + face, texture[1], 0);
glReadPixels(0, 0, kWidth, kHeight, GL_RED_INTEGER, GL_UNSIGNED_INT, outputValues);

Compute shader is very simple, imageLoad content from texture[0], and imageStore content to texture[1]. Does need to sync after dispatchCompute?

• My question: is it possible to transform multiple angular velocities so that they can be reinserted as one? My research is below:

• I have this code below in both my vertex and fragment shader, however when I request glGetUniformLocation("Lights[0].diffuse") or "Lights[0].attenuation", it returns -1. It will only give me a valid uniform location if I actually use the diffuse/attenuation variables in the VERTEX shader. Because I use position in the vertex shader, it always returns a valid uniform location. I've read that I can share uniforms across both vertex and fragment, but I'm confused what this is even compiling to if this is the case.

#define NUM_LIGHTS 2
struct Light
{
vec3 position;
vec3 diffuse;
float attenuation;
};
uniform Light Lights[NUM_LIGHTS];

• By pr033r
Hello,
I have a Bachelor project on topic "Implenet 3D Boid's algorithm in OpenGL". All OpenGL issues works fine for me, all rendering etc. But when I started implement the boid's algorithm it was getting worse and worse. I read article (http://natureofcode.com/book/chapter-6-autonomous-agents/) inspirate from another code (here: https://github.com/jyanar/Boids/tree/master/src) but it still doesn't work like in tutorials and videos. For example the main problem: when I apply Cohesion (one of three main laws of boids) it makes some "cycling knot". Second, when some flock touch to another it scary change the coordination or respawn in origin (x: 0, y:0. z:0). Just some streng things.
I followed many tutorials, change a try everything but it isn't so smooth, without lags like in another videos. I really need your help.
My code (optimalizing branch): https://github.com/pr033r/BachelorProject/tree/Optimalizing
Exe file (if you want to look) and models folder (for those who will download the sources):
http://leteckaposta.cz/367190436
Thanks for any help...

• By Andrija
I am currently trying to implement shadow mapping into my project , but although i can render my depth map to the screen and it looks okay , when i sample it with shadowCoords there is no shadow.
Here is my light space matrix calculation
mat4x4 lightViewMatrix; vec3 sun_pos = {SUN_OFFSET * the_sun->direction[0], SUN_OFFSET * the_sun->direction[1], SUN_OFFSET * the_sun->direction[2]}; mat4x4_look_at(lightViewMatrix,sun_pos,player->pos,up); mat4x4_mul(lightSpaceMatrix,lightProjMatrix,lightViewMatrix); I will tweak the values for the size and frustum of the shadow map, but for now i just want to draw shadows around the player position
the_sun->direction is a normalized vector so i multiply it by a constant to get the position.
player->pos is the camera position in world space
the light projection matrix is calculated like this:
uniform mat4 light_space_matrix; void main() { gl_Position = light_space_matrix * transfMatrix * vec4(position, 1.0f); } Shadow fragment shader:
out float fragDepth; void main() { fragDepth = gl_FragCoord.z; } I am using deferred rendering so i have all my world positions in the g_positions buffer
get_shadow_fac(light_space_matrix * vec4(position,1.0)); Where position is the value i got from sampling the g_position buffer
Here is my depth texture (i know it will produce low quality shadows but i just want to get it working for now):
sorry because of the compression , the black smudges are trees ... https://i.stack.imgur.com/T43aK.jpg
EDIT: Depth texture attachment:
glTexImage2D(GL_TEXTURE_2D, 0,GL_DEPTH_COMPONENT24,fbo->width,fbo->height,0,GL_DEPTH_COMPONENT,GL_FLOAT,NULL); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, fbo->depthTexture, 0);

• 13
• 16
• 10
• 17
• 9