Texture.cpp

#include"Texture.h"

Texture::Texture(const char* image, const char* texType, GLuint slot)
{
	// Assigns the type of the texture ot the texture object
	type = texType;

	// Stores the width, height, and the number of color channels of the image
	int widthImg, heightImg, numColCh;
	// Flips the image so it appears right side up
	stbi_set_flip_vertically_on_load(true);
	// Reads the image from a file and stores it in bytes
	unsigned char* bytes = stbi_load(image, &widthImg, &heightImg, &numColCh, 0);

	// Generates an OpenGL texture object
	glGenTextures(1, &ID);
	// Assigns the texture to a Texture Unit
	glActiveTexture(GL_TEXTURE0 + slot);
	unit = slot;
	glBindTexture(GL_TEXTURE_2D, ID);

	// Configures the type of algorithm that is used to make the image smaller or bigger
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST_MIPMAP_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

	// Configures the way the texture repeats (if it does at all)
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

	// Extra lines in case you choose to use GL_CLAMP_TO_BORDER
	// float flatColor[] = {1.0f, 1.0f, 1.0f, 1.0f};
	// glTexParameterfv(GL_TEXTURE_2D, GL_TEXTURE_BORDER_COLOR, flatColor);

	// Check what type of color channels the texture has and load it accordingly
	if (type == "normal") // prevents SRGB from deforming normals
		glTexImage2D
		(
			GL_TEXTURE_2D,
			0,
			GL_RGB,
			widthImg,
			heightImg,
			0,
			GL_RGBA,
			GL_UNSIGNED_BYTE,
			bytes
		);
	else if (type == "displacement")
		glTexImage2D
		(
			GL_TEXTURE_2D,
			0,
			GL_RED,
			widthImg,
			heightImg,
			0,
			GL_RGBA,
			GL_UNSIGNED_BYTE,
			bytes
		);
	else if (numColCh == 4)
		glTexImage2D
		(
			GL_TEXTURE_2D,
			0,
			GL_SRGB_ALPHA,
			widthImg,
			heightImg,
			0,
			GL_RGBA,
			GL_UNSIGNED_BYTE,
			bytes
		);
	else if (numColCh == 3)
		glTexImage2D
		(
			GL_TEXTURE_2D,
			0,
			GL_SRGB,
			widthImg,
			heightImg,
			0,
			GL_RGB,
			GL_UNSIGNED_BYTE,
			bytes
		);
	else if (numColCh == 1)
		glTexImage2D
		(
			GL_TEXTURE_2D,
			0,
			GL_SRGB,
			widthImg,
			heightImg,
			0,
			GL_RED,
			GL_UNSIGNED_BYTE,
			bytes
		);
	else
		throw std::invalid_argument("Automatic Texture type recognition failed");

	// Generates MipMaps
	glGenerateMipmap(GL_TEXTURE_2D);

	// Deletes the image data as it is already in the OpenGL Texture object
	stbi_image_free(bytes);

	// Unbinds the OpenGL Texture object so that it can't accidentally be modified
	glBindTexture(GL_TEXTURE_2D, 0);
}

void Texture::texUnit(Shader& shader, const char* uniform, GLuint unit)
{
	// Gets the location of the uniform
	GLuint texUni = glGetUniformLocation(shader.ID, uniform);
	// Shader needs to be activated before changing the value of a uniform
	shader.Activate();
	// Sets the value of the uniform
	glUniform1i(texUni, unit);
}

void Texture::Bind()
{
	glActiveTexture(GL_TEXTURE0 + unit);
	glBindTexture(GL_TEXTURE_2D, ID);
}

void Texture::Unbind()
{
	glBindTexture(GL_TEXTURE_2D, 0);
}

void Texture::Delete()
{
	glDeleteTextures(1, &ID);
}