1) textureProjOffset used
VERT:
#version 330
#extension GL_ARB_separate_shader_objects : enable
uniform mat4 modelMatrix;
uniform mat4 viewMatrix;
uniform mat4 projMatrix;
uniform mat4 shadowViewMatrix;
uniform mat4 shadowProjMatrix;
uniform sampler2DShadow shadowTex;

layout(location = 0) in vec4 vertex;

out vec4 vertexLight;
void main()
{
	gl_Position = projMatrix * viewMatrix * modelMatrix * vertex;
	vertexLight = shadowProjMatrix * shadowViewMatrix * modelMatrix * vertex;
}

FRAG:
#version 330
#extension GL_ARB_separate_shader_objects : enable
uniform mat4 modelMatrix;
uniform mat4 viewMatrix;
uniform mat4 projMatrix;
uniform mat4 shadowViewMatrix;
uniform mat4 shadowProjMatrix;
uniform sampler2DShadow shadowTex;

in vec4 vertexLight;
out vec4 color;

void main()
{
	const mat4 bias = mat4(
		0.5, 0.0, 0.0, 0.0,
		0.0, 0.5, 0.0, 0.0,
		0.0, 0.0, 0.5, 0.0,
		0.5, 0.5, 0.5, 1.0);

	vec4 shadowTexCoords = vec4(vertexLight.x,vertexLight.y,vertexLight.z-0.001,vertexLight.w) / vertexLight.w;
	shadowTexCoords = bias * shadowTexCoords;
	float shadeFactor = textureProjOffset(shadowTex, shadowTexCoords, ivec2(0.0));
	shadeFactor += textureProjOffset(shadowTex, shadowTexCoords, ivec2(1, 0));
	shadeFactor += textureProjOffset(shadowTex, shadowTexCoords, ivec2(-1, 0));
	shadeFactor += textureProjOffset(shadowTex, shadowTexCoords, ivec2(0, 1));
	shadeFactor += textureProjOffset(shadowTex, shadowTexCoords, ivec2(0, -1));
	shadeFactor /= 5.0;

	float shadowAttenuation = 1;
	if(shadeFactor < 0.5) shadowAttenuation = 0.5;
	color = vec4(1,0,0,1) * shadowAttenuation;
}


2) textureProjOffset unused
VERT: same as before

FRAG:
#version 330
#extension GL_ARB_separate_shader_objects : enable
uniform mat4 modelMatrix;
uniform mat4 viewMatrix;
uniform mat4 projMatrix;
uniform mat4 shadowViewMatrix;
uniform mat4 shadowProjMatrix;
uniform sampler2DShadow shadowTex;

in vec4 vertexLight;
out vec4 color;

void main()
{
	const mat4 bias = mat4(
		0.5, 0.0, 0.0, 0.0,
		0.0, 0.5, 0.0, 0.0,
		0.0, 0.0, 0.5, 0.0,
		0.5, 0.5, 0.5, 1.0);

	vec4 shadowTexCoords = vec4(vertexLight.x,vertexLight.y,vertexLight.z-0.001,vertexLight.w) / vertexLight.w;
	shadowTexCoords = bias * shadowTexCoords;
	float shadeFactor = textureProj(shadowTex, shadowTexCoords);
	shadeFactor += textureProj(shadowTex, shadowTexCoords);
	shadeFactor += textureProj(shadowTex, shadowTexCoords);
	shadeFactor += textureProj(shadowTex, shadowTexCoords);
	shadeFactor += textureProj(shadowTex, shadowTexCoords);
	shadeFactor /= 5.0;

	float shadowAttenuation = 1;
	if(shadeFactor < 0.5) shadowAttenuation = 0.5;
	color = vec4(1,0,0,1) * shadowAttenuation;
}